Concept Development of a New
System for Drying Dishware
Degree project for Bachelor of Science in Innovation and Design Engineering
Konceptutveckling av ett nytt system för torkning av disk
Examensarbete inom högskoleingenjörsprogrammet innovationsteknik och design
Ossian Bergman
Faculty of Health, Nature and Engineering Science
Degree project for Bachelor of Science in Innovation and Design Engineering Bachelor Thesis, MSGC12, 22.5 credits
Supervisor: Monica Jakobsson Examinator: Leo de Vin Date: 2020-06-07
Abstract
The Drying of dishware inside a dishwasher is the phase in the washing cycle that uses the most energy and is therefore the phase with most room for improvement as regards on energy usage. When drying the dishware through closed air circulation, it is the temperature of the final rinse that determines the heat available during the drying process. If heat from the final rinse is to be used more efficiently, how could such a concept of drying be developed?
The project was directed as a process for product development. To gain a better understanding of the problem, the project started with a pre study which include the issues: how does drying with air work, how is drying done in today’s dishwashers, how does other industries solve this problem? The pre study is later summarized in a requirement specification, that describes what demands and wishes there are for the concept.
To easier understand the big complex problem, it was branched out into smaller sub problems, with the goal of coming up with ideas for each sub problem, and later combine them into concepts using a morphological matrix. With the requirement specification as a starting point, ideas were generated for each sub problem, with the creative methods brainstorming, brain- writing and SCAMPER.
The chosen solution consists of a tray combined with a system of air circulation. The tray is drawn up under the upper basket from the side of the dishwasher. It then collects the water dripping down from the dishes above, preventing the water from dripping onto the lower basket, and therefore leaving less water on the dishes below. Thereafter the tray is retracted when the water is done dripping, and the water runs off the tray, along the wall. The air circulation is then activated and directed from the top towards the bottom. This removes the leeward between the dishware and the basket that otherwise appears because the air reaches the basket first.
The air circulation system is designed with the risk of flooding in mind. That resulted in a drainage system that traps all the water that manages to get inside the system and drains it back into the washing space. Further, ribs were integrated into the inlet to prevent the water from spraying straight into the system. The ribs also help spread the air where it is needed.
Sammanfattning
Torkning av disk inuti en diskmaskin är den fas som kräver mest energi, vilket innebär att torkningen är den del som innehar störst rum för förbättringar med hänsyn till
energianvändning. Vid torkning av disk med en stängd luftcirkulation är det temperaturen på den sista sköljningen som avgör hur mycket värme som finns tillgängligt under torkningen.
Därav gäller det att använda den effektivt, så hur kan ett koncept se ut för att använda värmen effektivare?
Projektet har utförts efter en process för produktutveckling. Projektet inleddes med en förstudie för att få en bättre förståelse över problemet, som bland annat innefattar frågorna:
hur torkning med luft fungerar, hur ser torkningen ut i diskmaskiner idag, hur har problemet med torkning lösts inom andra områden? Förstudien sammanfattades i en kravspecifikation som beskriver vilka krav och önskemål som finns för slutkonceptet.
För att enklare förstå det problemet grenades det ut i flera delproblem, med syftet att hitta lösningar för varje delproblem och sedan koppla ihop dem till koncept genom en morfologisk matris. Med kravspecifikationen som startpunkt genererades olika lösningsalternativ fram för varje delproblem, med kreativa metoderna brainstorming, brain-writing och SCAMPER.
Det valda konceptet består av en gardinlösning tillsammans med ett luftcirkulationssystem.
Gardinlösningen skjuts in under övrekorgen, från sidan av diskmaskinen. Gardinen samlar där upp det vatten som rinner av den övre korgen för att hindra det från att droppa på den undre korgen. Gardinen förs ner igen när vattnet droppat klart, och det som fångats rinner av gardinen, längs väggen. Luftcirkulationen aktiveras sedan och är riktad från taket mot botten.
Detta tar bort den läsida mellan korg och disklast som annars uppstår till följd av att luften når korgen först.
Luftcirkulationen designades med risken för översvämning i tanken. Det ledde till ett
dräneringssystem som fångar vattnet som lyckats ta sig in i systemet och leder det tillbaka in i diskutrymmet. Ytterligare monterades ribbor som förhindrar vattnet från att spruta rakt in i systemet. Ribborna hjälper också till att sprida luften dit där den behövs.
Table of Content
Abstract...3
Sammanfattning ...4
1. Introduction ...7
1.1 Background ...7
1.2 Problem formulation ...8
1.3 Purpose ...8
1.4 Goal ...8
1.5 Delimitations ...8
2. Methodology ...9
2.1 Project plan ...9
2.1.1 Time Plan ...9
2.1.2 Risk Analysis (Mini Risk Method) ...9
2.2 Research ... 10
2.2.1 Literature Studies ... 10
2.2.2 Environmental Impact examination (EPD) ... 10
2.2.3 Competitor Product Analysis ... 11
2.3 Requirement Specification ... 11
2.4 Function Structure ... 12
2.5 Creative Methods ... 12
2.6 Concept Selection ... 14
2.6.1 Paired Comparison of the wishes ... 14
2.6.2 Elimination Matrix ... 14
2.6.3 Pugh Matrix ... 15
2.6.4 SCAMPER ... 15
2.7 Failure Modes and Effects Analysis (FMEA) ... 16
2.8 Detailed Concept Development ... 17
3. Results ... 18
3.1 Project Plan ... 18
3.1.1 Time Plan ... 18
3.1.2 Risk Analysis ... 19
3.2 Research ... 20
3.2.1 Literature Studies ... 20
3.2.2 Environmental Product Declaration (EPD) ... 22
3.2.3 Competitor Product Analysis ... 22
3.3 Requirement Specification ... 24
3.4 Function Structure ... 25
3.5 Creative Methods ... 26
3.6 Concept Selection ... 35
3.6.1 Paired Comparison... 35
3.6.2 Elimination Matrix ... 35
3.6.3 Pugh Matrix ... 36
3.6.4 SCAMPER ... 37
3.7 Final Concept Selection ... 38
3.8 Failure Modes and Effects Analysis, FMEA ... 40
3.9 Detailed Concept Development ... 41
4. Discussion ... 51
5. Conclusion ... 53
Appendix I – Project Plan ... 58
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1. Introduction
1.1 Background
ASKO (n.d.b) Appliances AB is known for producing and developing appliances of high quality with their Scandinavian touch on looks and functionality. ASKO have been producing appliances for 70 years with the goal to live up and exceed the customer expectations for many years to come. With this said they are producing appliances of highest standards. ASKO have observed that drying of the dishware within the dishwasher have become a factor that customers consider when purchasing a new appliance as well as there are plenty opportunities to make it more efficient. To gain input from a new perspective how this could be solved, the project was carried out as independent as possible, although if the project would head in the wrong direction ASKO would steer it back.
Drying systems has evolved from closed door condensation drying and zeolite absorption systems to auto door opening systems. Each of them having their own disadvantages and advantages. ASKO have identified that future techniques for high performance drying demands more air circulation within the closed dishwasher to make a difference.
The process of drying has been defined by Keey (1992) as one in which moisture is vaporized from a material and thereafter swept away with a gas that passes by either its surface, through it and/or over it. Minde (2011) describes that up to 60% of the dishwasher’s total energy usage occur during its drying cycle. Therefore, drying of dishes is the phase to start examine when trying to improve with regards on energy usage. Further Minde (2011) define drying systems as either dynamic or static. Whereas a static system does not use any additional component to force the air circulation, although, on the other hand a dynamic system forces a circulation.
The drying process in a dishwasher consist of convection and the drying effect that appears from the gravity pulling the water off. Eventually the mass of the water is too small which leads to the surface tension exceeding the gravity. Then the drying must be done by convection.
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1.2 Problem formulation
How can better drying be achieved within the closed dishwasher?
1.3 Purpose
Design and develop a conceptual system for more uniform air-drying within the closed dishwasher to improve the drying of the contained dishware. A new system that can dry the dishware more efficient will make it possible to either lower the washing temperature and/or make the washing program shorter. That in return will lower the energy usage.
The purpose for the student is to learn more about managing a project with its associated parts and apply the collected knowledge during the education to real life projects.
1.4 Goal
The projects goal is to build a prototype of the developed concept for drying the dishware and mount it to a dishwasher to compare against the default drying value, which is available for each model. Plus create Computer Aided Design (CAD) models of the concept.
1.5 Delimitations
The delimitations the project will consider are:
• The load placement is defined by ASKO for every dishwasher.
• The Eco-design Directive (European standard EN 50242 2008) with supplied
standards, determine how a test load is composed, how clean and how dry it should be.
The method for assessing this is also defined by the European standard EN50242 (Anon. 2008).
• The developed system will only be tested with the “Eco-program” on the dishwasher.
• No Material selection will be done.
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2. Methodology
The project will follow the methodology for the product development process described by Johannesson et al. (2013). The methodology is an iterative process, and therefore some phases are repeated multiple times. In Figure 1 you can see a simplified version of the project’s main stages.
Figure 1. The project's main stages.
2.1 Project plan
A project plan was composed to have something to direct the project along (Tonnquist 2018).
The project plan includes a time plan and risk assessment as it should be enough for an outsider to understand the purpose and goal with the project.
2.1.1 Time Plan
A Work Breakdown Structure (WBS) was done to breakdown the project into small packages, to easier see what must be done to reach the set goal. The WBS however lack time- and order relationship (Eriksson & Lilliesköld 2004). A complement to the WBS are the Pert schedule, which provide a graphical representation of the project’s timeline with its parts as well as the critical path (Tonnquist 2018). These two methods together made up the time plan, which was visualized in a Gantt chart. The chart is a good and simple way to show the project’s different parts duration with start and finish dates (Johannesson et al. 2013).
2.1.2 Risk Analysis (Mini Risk Method)
The risk analysis was done according to the mini risk method. This method deals with the probability of qualitative and quantitative risks occurring and consider the consequences. In this method both the probabilities and consequences were evaluated and rated from one through five (Tonnquist 2018). The risk value was calculated by multiplying the likelihood with the consequence. By calculating a risk value, the risk became more measurable and relatable to real life.
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Table 1. Example of the mini risk method (Tonnquist 2018).
Risk
(L=Likelihood, C=consequence)
Likelihood 1 to 5
Consequence 1 to 5
Risk value L x C =
Risk response
The system is too slow. 2 2 4
Resource deficit for supplier
2 5 10 Draw up contracts.
Internal resource deficit 4 5 20 Sign on resources
well ahead of time
2.2 Research
2.2.1 Literature Studies
The literature study examined published scholarly articles, books and scientific reports that provide information related to the area of exploration. The purpose was to gain an overview of the relevant literature to the topic, to develop an opinion and perspective on the subject (Milton & Rodgers 2013). More in depth how the literature studies were done can be seen in Table 2.
Table 2. Sample of how the research was done.
Issue Search
Word
Search
Tool
Delimitation(s) Results
How does the drying work today?
air dry* closed circulation
OneSearch Drying
Dry air Circulation Convection Energy Heat Transfer
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To rehearse thermodynamics regarding the process of convection drying and which factors have the biggest impact, the books Energiteknik (Alvarez 2006) and Tillämpad termodynamik (Ekroth & Granryd 2006) were studied, especially the chapter regarding “Luftbehandling - Fuktig luft” in the book Energiteknik.
2.2.2 Environmental Impact examination (EPD)
An Environmental Product Declaration (EPD) performed by EU was examined to estimate and review the product’s total environmental impact during its lifecycle; to gain an
understanding how the drying process affects the environment. The EPD was carried out on
11 household dishwashers of 13 plate settings.
2.2.3 Competitor Product Analysis
A Competitor Product Analysis was done to identify the strengths and weaknesses of the competitors’ products; this method also determines the main competitor (Milton & Rodgers 2013). The competitors were identified in conversation with the supervisor at ASKO. As a result of the time and resources available only three competitors were included. When the competitors were identified, information regarding each product were found by visiting each of the competitors’ website.
2.3 Requirement Specification
The requirement specification should clarify what the project is supposed to deliver with specific requirements (Tonnquist 2018). Johannesson et al. (2013) describe that the
requirement specification will be the starting point when generating concepts. Therefor was the requirement specification done restricting but also distinct and not limiting. The
requirement specification was the final part for the pre study phase of the project.
Olsson’s Criteria Matrix
Olsson’s criteria matrix was used to systematically come up with criterions for each cell in the matrix to implement in the criteria matrix (Johannesson et al. 2013). The rows consist of the products lifecycle phases and the columns different aspects/stakeholders, see Table 3.
Table 3. Olsson's Criteria Matrix (Johannesson et al. 2013)
Lifecycle phase Aspects
Process Environment Human Economy Creating (development, construction
etcetera)
1.1 1.2 1.3 1.4
Production (manufacturing, assembly, storage etc.)
2.1 2.2 2.3 2.4
Distribution (sales, etc.) 3.1 3.2 3.3 3.4
Usage (installation, maintenance etc.) 4.1 4.2 4.3 4.4
Disposal (recycle, destruction, etc.) 5.1 5.2 5.3 5.4
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2.4 Function Structure
To understand the products complex total function, it was divided into subfunctions to see how they cooperate. The purpose with this method was to find concept solutions that fulfils each of the subfunctions. This is easier than finding a total solution to the big complex problem (Johannesson et al. 2013).
Figure 2. Example of a function structure for a product with main function "Wash clothes" (Johannesson et al. 2013).
2.5 Creative Methods
BrainstormingThe idea generating method brainstorming is a well-tested and strictly written method.
Brainstorming works best with a group of 5-15 people, which motivates each other to come up with new ideas and combine them, the keyword is quantity over quality (Johannesson et al.
2013). There are some ground rules for the method:
• No critique allowed
• Quantity over quality
• Go outside the box
• Combine ideas
The brainstorming was first done single handed. Thereafter it was done in a group of 7 students to gain inspiration from each other’s ideas. The brainstorming was based on three issues:
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• How can a more even drying be achieved during the “runoff” phase?
• How can the remaining water be dried?
• How can the remaining water be dried by air?
Brain-writing
Brain-writing was used in addition to brainstorming. The method involved the same group of 7 students. Each person thought up to 3 ideas every 2 minutes. The sketching were done on the same paper. According to Litcanu et al. (2015) shall all sketches be done on the same paper, to let the participants be inspired by each other’s solution to come up with new ideas.
Because the method is done in silence the effects of status differentials, conflicts and norms are being eliminated.
The issues assessed with Brain-writing were the same as the brainstorming’s issues.
Morphological Matrix
To combine multiple sub solutions into a complete concept, a Morphological Matrix was used. The systematic method Morphological matrix works as shown in Table 4. Johannesson et al. (2013) describe the method as a good tool to minimize the risk of overlooking a
combination.
Table 4. Example of a morphological matrix for product with total function "keep the food at a low temperature"
(Johannesson et al. 2013).
Subfunction Subfunction solutions
Contain food Volume with rectangular cross section
Spherical volume
Isolated bag -
Keep the temperature
Compressor system
Dry ice filling “Hole in the ground”
The house’s heat pump system
Grant access Door Jalusi Sliding door -
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2.6 Concept Selection
2.6.1 Paired Comparison of the wishes
Paired comparison is a good method for avoiding subjective evaluation of the different wishes by giving them a value (Johannesson et al. 2013). The criterias were added to an array, in both its rows and columns as Table 5 shows. In the paired comparison the two criterias split the value 1. The criteria that is more important received the value 1 or if they are equally important both were set to 0,5.
Table 5. Value determination matrix (Johannesson et al. 2013)
Criteria A B C D E F Sum Sum/Tot
Wish A - 0 0 0.5 1 - 1.5 0.10
Wish B 1 - 0 0.5 1 0.5 3.0 0.20
Wish C 1 1 - 0.5 1 0.5 4.0 0.27
Wish D 0.5 0.5 0.5 - 0.5 0.5 2.5 0.17
Wish E 0 0 0 0.5 - 0 0.5 0.03
Wish F 1 0.5 0.5 0.5 1 - 3.5 0.23
Total 15.0 1.00
2.6.2 Elimination Matrix
To separate the bad ideas or ideas that need more investigation an elimination matrix is used as it is a good method for an initial evaluation (Johannesson et al. 2013).
Table 6. Elimination Matrix by Pahl and Beitz (Johannesson et al. 2013).
Page Elimination matrix for: Elimination criteria:
[+] Yes [-] No
[?] More info needed
[!] Verify requirement specification
Solution Solves the main problem Meets the requirements Feasible Under cost ceiling Safety and ergonomics Fits the company Enough information
Decision:
[+] Pursue solution [-] Eliminate solution [?] Seek more info
[!] Verify requirement specification
Comment Decision
1 + + + + + + + +
2 + + - -
3 + + ? + + + + !
4
15 The alternative solutions marked with “+” goes straight on to the next evaluation round.
Those that need more information are marked with “?”, and those marked with “-“ will be eliminated. If the solution receives “!” it have to be verified against the requirement specification.
2.6.3 Pugh Matrix
The final evaluation was done using a Pugh matrix, this matrix works similar as the elimination matrix, except the existing system Turbo Drying Express was added as a
reference to compare the concepts against. Johannesson et al. (2013) describe that the matrix works as follows: Every solution is compared to the reference and then considered if the actual solution attains the criteria better, equally, or worse than the reference. Afterwards the results are summed to allow for arranging the solutions from best to worst. With this
knowledge the solutions with only 0’s or equal “+” as “-“ be reviewed to determine which of those that are best.
Table 7. Relative decision matrix according to Pugh (Johannesson et al. 2013).
Criteria Alternatives
1 [ref] 2 3 4 5
Wish A D
A T U M
- + 0 -
Wish B + + - +
Demand D 0 - - +
Wish E - 0 - +
Sum [+] 1 2 0 3
Sum [0] 1 1 1 0
Sum [-] 2 1 3 1
Net value 0 -1 1 -3 2
Ranking 3 4 2 5 1
Proceed yes no yes no yes
2.6.4 SCAMPER
The exercise SCAMPER was executed on the 3 best concepts according to the Pugh Matrix.
SCAMPER is a method to challenge solutions by looking at them with a different perspective.
Is it possible to remove anything, solve the problem with another solution, or change parts of the solution/idea (Stiftelsen Svensk Industridesign [SVID] n.d.)? Further SVID (n.d.)
describes the letters in SCAMPER as following:
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• Substitute
• Combine
• Adapt
• Modify
• Put to use, change area of use
• Eliminate
• Reverse
Examples of questions that were used are: what could make it better? What else can use this product? What if you combined it with a different purpose?
During the examination of the 3 concepts a timer was set for 5 minutes per question stated in SCAMPER, to not lose focus.
2.7 Failure Modes and Effects Analysis (FMEA)
The system consists of several sub solutions and components that is set together in such way that they together perform according to the requirement. The main concern when putting these sub solutions together are to identify potential failures and to prevent these from occurring (Rausand & Høyland 2004). To easier branch out the functions with highest risks a column Risk Value were added. By multiplying the Failure rate with the Severity ranking the Risk Value was calculated. That means the functions with highest Risk Value are the ones most prone to fail when putting the sub solutions together. The method FMEA was used to identify these potential failure modes of each sub solution and the effects these failures could have on the system.
Table 8. A modified FMEA sheet from Rausand & Høyland (2004).
Description of unit Description of failure Effect of failure Failure rate
Severity ranking
Risk Value
Risk reducing measures
Comments Ref.
No
Function Opera tional mode
Failure mode
Failure cause or mechanism
Detection of failure
On the subsystem
On the system function
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2.8 Detailed Concept Development
Detailed Concept Development using sketches
To start detail develop the chosen concept, more detailed sketches were done to help visualize a more specific solution. Roam (2009) describes the mind and its thoughts as fluid where everything floats together perfectly. Because of this, the sketches usually do not turn out as expected. Therefore, it is good to start with sketches which allows to go back easily. In
addition to helping visualize the solution, the sketches give a base to start the Computer Aided Design (CAD).
Computer Aided Design (CAD)
CAD was implemented because of multiple reasons when designing. According to Narayan et al. (2008) CAD is a good tool for:
• Increased productivity by helping to visualize the product and its sub assemblies which reduce the time spent synthesizing, analysing as well as documenting the design. In total this shortens the time spent during a design project.
• Improve quality with the CAD systems capability to do a thorough engineering analysis within a shorter period of time. The program also calculate with a better accuracy which means the risks and errors with the design are reduced. This leads to better quality and accuracy with the design.
• Database for manufacturing
When modelling the design in the CAD program most of the database required to program an additive manufacturing device to manufacture the component is created simultanously.
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3. Results
In this chapter all the results from the methodology will be presented.
3.1 Project Plan
The complete project plan is attached in appendix I. Where you can see the Gantt-scheme for example.
3.1.1 Time Plan
The project was broken down into the following sections as seen in Figure 3. The report was written parallel to the project’s progression
Figure 3. Work Breakdown Structure for the project.
19 The projects critical path and the different parts impact on each other can be seen in the Pert schedule in Figure 4. The critical paths edge is highlighted red and calculated to be 51 days.
Since the project was done by one person the schedule ended up straight.
3.1.2 Risk Analysis
The risk assessment was made according to the Mini Risk Method. A risk that occurred by the half-time mark of the project is Covid-19. The most severe consequence of Covid-19 was that social distancing became a high priority/a must, which limited the possibilities to have tutor meetings, availability of the workshop, visits at ASKO, work on the project at school, library opening hours etc.
Figure 4. Pert scheme.
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Table 9. Risk analysis for the project.
No. Risk Probability
[1–5]
Consequence [1–5] Risk factor [PxC]
Preventive adjustment
Consequence measure
1 Time management does not hold up for some reason.
2 4 8 Work actively and
have a good communication with supervisors.
Book a meeting with supervisors to sit down and reflect over how it came to this, and how to continue the project.
2 Bad communication with customer and/or supervisors.
1 5 5 Have a regular
contact with the customer.
Actively meet the customer and book meetings in advance.
3 Bad documentation. 1 5 5 Take as many
pictures as possible and regularly save files to OneDrive and hard drive.
Go back to the latest saved document and try to fill out the blank, that was lost.
4 Illness. 2 5 10 Always keep
everyone up to date and have multiplate contacts within the customer company.
Reschedule the different parts of the project, and make sure to always work forcibly.
5 Not enough
knowledge about the required subject.
3 5 15 Have plausible
delimitations.
Ask supervisors and/or employees at the company for assistance.
6 Failure of
computer/program.
1 4 4 Regularly save
work to OneDrive and several hard drives.
Download the files from OneDrive to another computer.
7 The developed solution does not meet the set requirements.
2 4 8 Regularly discuss
with the customer about the solution.
Write down which requirements the solution did not meet and how future work with the solution could be executed.
8 Covid-19 spread to Sweden.
3 4 12 Upload everything
to the cloud and do the pre study thorough enough that the project can be completed without any tests.
Follow the
recommendations from the authorities and complete the project but on a more theoretical basis.
3.2 Research
3.2.1 Literature Studies How does the dishwasher work?
ASKO currently have three existing solutions for drying dishware: Turbo Drying, Turbo Combi Drying and Turbo Drying Express. The Turbo Drying works by actively evacuate the humid air with a fan at the top of the dishwasher and later open the door automatically. Turbo Combi Drying works similarly as the former although this solution additionally extracts the moist from the moist air and guide the condensed water into the machine again. The latter
21 solution works in the same fashion except that it has an additional fan at the bottom of the dishwasher which draws in hot steam. This steam is then removed with the other fan before it cools down and dripples down on the dishware (ASKO n.d.a).
A dishwasher is mainly made up of seven parts: a transceiver device to monitor everything, a slug removal device, main cleaning device (the spinning rotors), a motor/pump, water supply, heating element and drainage device 1.
When drying dishware within a closed dishwasher equipped with a closed air circulation system, the major factor for the dishes drying result is the final rinse temperature (Jeong &
Lee 2014). Because the air circulation is closed, the final rinse temperature determines the heat available during the drying.
Different types of drying and/or dealing with condensation
Vacuum drying – Better suitable for heat-sensitive materials/objects. By lowering the
surrounding pressure, the water boils (evaporates) at a much lower temperature, therefor more energy efficient. Requires a vacuum pump, condenser, and a heating element (Zhang et al.
2018).
Air drying (convective and diffusion) – According to Alvarez (2006) the phenomenon drying consist of two parts, diffusion, and convection, where the fastest and easiest part to alter is the convection. The dominant factors when drying is the flow of the fluid, the surface area of what is being dried as well as the temperature difference from the solid “wall” and the fluid.
Freeze-Drying – This method is best suitable for heat-sensitive objects such as food. The item to be dried gets frozen at atmospheric pressure, later the pressure is decreased which makes the frozen water sublimate (Patel et al. 2010)
Tumblers are divided into two different categories according to Brunzell (2006) – Open cycle dryer heats up the air from the room which it then leads into the drum, the air is later
evacuated out of the building.
Closed cycle dryer works in such way that the air is recirculated inside the dryer itself. The air from the drum is lead through a heat exchanger where the moist in the air is condensed. When
1 Mikael Johansson Engineer ASKO, interview 9th March.
22 the air is dry it is heated and forced into the drum again.
3.2.2 Environmental Product Declaration (EPD)
According to Boyano et al. (2017) a dishwasher with the size of 13 place settings emits 1895 kg CO2 under its lifecycle of 12,5 years. Most of the emissions occur during the usage phase:
1525kg. The production emits 360kg and the end-of-life phase absorb 29 kg. During the usage phase 60 % of the emissions occur because of drying the dishware (Minde 2011). This means that the drying phase is the phase to start examine when for improvement regarding energy efficiency.
3.2.3 Competitor Product Analysis Top competitors:
• Bosch
• Electrolux *
• Siemens
* main competitor
Products/systems
• Bosch, Siemens – Zeolith, comes with the more expensive appliances.
• Electrolux – AirDry, comes with a large variety of machines. Ranging from 4780 SEK to 10990 SEK.
Technology
• The Zeolith system works as an anti-moist system. The system sucks in the cold, moist air and converts it into hot, dry air. When the zeolite beads get in contact with moist it adsorbs the moist which it turns into heat (Siemens n.d.). A chemical reaction bonds the water atoms to the zeolite minerals surface, which in return releases heat. To
“recharge” the zeolite, to make it able to adsorb more water next time, at the beginning of the next washing cycle, the dishwasher heat up the zeolite stones at the same time as the dishes, which lets the stones release its moist. This in its turn “discharges” the stones (Brezinski 2019).
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• AirDry technology is less advanced than the Zeolith system. The technology can be summarized as when the hot water for drying has been injected the machine let the dishes cool down to the “right” temperature. When the temperature has been reached, the machine opens its door 10cm, to let the hot air escape, and let cold air in. This together creates a natural airflow, which dries the dishes (Electrolux n.d.).
Pros and Cons The Zeolith system
Table 10. Pros and Cons for the Zeolith system.
Pros Cons
Energy efficient. A 12-setting machine without the system uses 290 kWh, to a 14- setting machine that uses 237 kWh.
For now, it is an expensive system because of the availability of the zeolite granules.
It dries the dishes very efficient and good.
AirDry
Table 11. Pros and Cons with the AirDry system.
Pros Cons
Cheap compared to other drying systems. Require a high amount of energy to perform as good as other solutions.
Not as energy efficient as the zeolith system.
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3.3 Requirement Specification
A criteria matrix was compiled from Olsson’s criteria matrix. The criterions under the different subjects were determined in conversation with ASKO and concluded from the pre study.
Table 12. Criteria Matrix based on Olsson's Matrix.
Nr. Cell Criteria D = Demand
W = Wish
F = Functional L = Limitation
1 1.1 A more even drying within the dishwasher. MF L
2 1.1 Closed air circulation system. W, 4 L
3 1.1 Solution shall not make the dishwasher larger. D L
4 1.1 Do not interfere with loading capacity. D L
5 1.2 Energy efficient. W, 3 F
6 1.2 Smart construction to minimize weight and material use.
W, 2 F
7 1.3 Non-toxic materials for humans. D L
8 1.3 No risk of over-heating on the dried dishes/system. D L 9 2.3 System contains few components as possible.
Value = N/A
W, 3 F
10 3.1 Delivered installed within the dishwasher. D L
11 3.2 No major additional weight, that decrease the number of dishwashers able to be transported at once.
W, 2 F
12 4.1 Improved drying in the corners compared to old drying system.
W, 5 L
13 4.1 Do not release hot and moist air to the surroundings. D L 14 4.1 Operate with a volume under 60 dB(A) W, 2
15 4.1 Do not let dirt into the system during the washing cycle.
D L
16 4.2 Maintenance free system. W, 3 F
17 4.2 Withstand water. D L
18 4.2 Withstand detergent. D L
19 4.2 Withstand milk fats from dishes. D L
20 4.3 Visible solution for the customer. W, 1 F
21 4.4 Lifecycle of 20 years (5600 cycles). W, 2 L
22 5.1 Easy dismantling, without the need of special tools. W, 2 L
23 5.2 100% recyclable W, 2 L
24 5.3 No hazardous substances when dismantling/recycling
D L
25 5.4 The recycled material should pay for the cost of dismantling
W, 2 L
25
3.4 Function Structure
The problem was divided into the subfunctions: Enhance the runoff, lead in dry air, initiate forced convection with improved air circulation and lead away moist air which can be seen in Figure 5. The different subfunctions was determined by studying the thermodynamics of drying, the existing drying solution and looking at the results of a drying test.
By studying the results of a drying test, the drying process in a dishwasher could be divided into two steps. The runoff and the convective drying. This could be determined because the driest dishware is always at the top, even though different elements were added, such as an air-heater. The extra components mostly improved the wet areas, which were the lower placed dishware.
Figure 5. Function Structure of drying system within the dishwasher.
26
3.5 Creative Methods
Brainstorm
The brainstorming sessions single-handed generated a vast variety of ideas under the three different issues: How to enhance runoff, how to dry the remaining water, how to dry the remaining water with air? Where the latter issue was the hardest to come up with solutions for. This process was later repeated with the group of students. The group also thought the last issue were the most challenging. Some ideas that were generated during the single-handed sessions also came up during the group session, which reinforce the ideas.
The ideas to the left in Figure 6 both incorporate a tray that prevent the water from dripping onto the lower basket, to reduce the amount of water on the dishes below. The idea to the right consists of a reversed air circulation reduce the leeward between the basket and dishes.
Figure 6. A sample picture of three ideas generated during the brainstorming session.
27 Brain-writing
By letting the group take inspiration from each other, a hand full of new ideas were born. Especially during the last round of brain-writing where a random word (rubber tire, serpentine road, projector, and rock bunting) was said as the round started. It can be seen on the sketches that the group took inspiration from these random words, see Figure 7 to see how serpentine road inspired some solutions. Serpentine road led to solutions that consist of a small strip with holes in it that covered a side of the dishwasher.
Morphologic Matrix
The reason for leaving the rows “Lead in/away air” blank is that it is not a significant part for solving the problem. These subfunctions are easy to solve and will be done based on the needs from the chosen concept.
Before the Morphological Matrix was implemented, the ideas generated through the creative methods were summarised into different categories of solutions. Further the unreasonable ideas were sorted out.
Figure 7. A sheet with ideas from the brain- writing session.
28
Figure 8. Morphological Matrix without the links.
Figure 9. Morphological Matrix with the sub solutions paired together.
29 The intention with the matrix was to pair sub-solutions together, to come up with complete concepts that could achieve a more even drying in the dishwasher. The number of concepts that were extracted from the matrix were limited to 10, in combination of limiting the concepts to only one enhancer/enabler to prevent the concept selection from being too time consuming.
The solutions derived from the morphological matrix will be evaluated under chapter 3.7-3.10
30 Concept 1.
The first concepts’ runoff enhancer consists of movement. The dishware/basket gain
momentum that exceeds the surface tensions of the water by vibration, which means smaller water droplets will be able to run off the dishes, which results in more water runs off.
Thereafter when the surface tension cannot be surpassed by the vibrations, the dish arms will initiate an air circulation by letting out air instead of water, with the aid of a coupling within the dish arm. This sub solution is supposed to act as a snow cannon, which can blow out air and water by the help of its coupling. This solution could potentially be enhanced by hanging the cups for example.
Figure 10. Picture showing the sub solutions concept 1 consists of.
Concept 2.
This concept’s runoff enhancer incorporates the vibration solution; however, the convection is forced by having the whole side of the dishwasher turned into an inlet for the pulling fan (see Figure 11). As a result of having the whole side being an inlet and having the outlet on the opposite side the air will travel a shorter distance and allow for a bigger air flow since the total size of the outlet and inlet are increased, thus increasing the convection. By rotating the dishware 90° the air flow is parallel to the dishes which increases the air flow.
Figure 11. Picture showing the sub solutions concept 2 consists of.
31 Concept 3
Alike the earlier mentioned concepts, this concept relies on vibrations to allow for smaller droplets to runoff. For improved convection drying, the air circulation’s direction has been changed. With the air direction being changed the leeward between the dishware and the basket is removed, due to the air first getting in contact with the dishware and then the basket;
therefore, no water is trapped and less surface of the dishware in the leeward. The downside of changing the air flows’ direction, is that moist air have a lower density than dry air (Herrmann et al. 2009). The result of this is that the moist air will rise, and work against the air flows’ direction. The dishware could be rotated to improve the air flow.
Figure 12. Picture showing the sub solutions concept 3 consists of.
Concept 4
By applying a surfactant to the water its surface tension decreases. With a decreased surface tension more water can runoff the dishware. A lower surface tension also increases the convection by letting the water spread out on a larger area (Alravez 2006). The air circulation is reversed in this concept as it is in concept 3. The dishware is rotated to improve the air circulation.
Figure 13. Picture showing the sub solutions concept 4 consists of.
32 Concept 5
As concept 4, this concept uses the surfactant to enhance the runoff. However, this system’s air circulation consists of the whole side turned into an inlet. The whole side of the
dishwasher is an inlet, and the outlet is on the opposite side. This concept can be enhanced by hanging the cups and glasses to minimize contact area.
Figure 14. Picture showing the sub solutions concept 5 consists of.
Concept 6
In this solution the runoff water is captured in a tray that prevents the water from dripping down onto the lower basket filled with dishware. This means there is an even amount of water to dry by convection on the upper basket and the lower basket. For this reason, the lower baskets dishware will be dryer. Therefore, a more even drying will be achieved resulting in a higher drying score. The convective drying is forced by having the whole side of the
dishwasher as an outlet. This concept can be enhanced by lowering the pressure in the washing space.
Figure 15. Picture showing the sub solutions concept 6 consists of.
33 Concept 7
This concept utilises the catching tray like the previous concept, although the convection drying unit is now integrated into the basket. The wiring in the basket is made hollow, with little holes in it. The air will be blown into the baskets wiring and then “escape” out of the small holes, directly onto the dishware. This results in every piece of the load having more air passing by and less surface area in leeward. This concept could utilize pressure in the washing space to lower the evaporation temperature.
Figure 16. Picture showing the sub solutions concept 7 consists of.
Concept 8
The basket solution is included in this concept to stop the water from dripping onto the lower basket. The air circulation is reversed to remove the leeward between the dishware and basket. A vacuum pump could be used here to lower the pressure in the washing space.
Figure 17. Picture showing the sub solutions concept 8 consists of.
34 Concept 9
To enhance the runoff the air circulation is reversed to aid the gravity in pulling the water off.
In addition to the reversed air circulation the outlet is made larger to spread the air. To improve the air circulation’s flow the dishware is rotated 90.
Figure 18. Picture showing the sub solutions concept 9 consists of.
Concept 10
To get a more even drying process in the dishwasher the lower and upper basket are divided into two separate smaller spaces. This prevents the upper basket’s water to drip down on the lower basket. To dry off the remaining water the baskets piping idea is used to focus the air circulation onto every piece of the load. The drying could be enhanced by pressurizing the washing space.
Figure 19. Picture showing the sub solutions concept 10 consists of.
35
3.6 Concept Selection
3.6.1 Paired Comparison
By doing a paired comparison of the different wishes in the criteria matrix, the six most valuable wishes were determined, which later were implemented to the Pugh Matrix.
Improved drying in the corners (number 12) and closed air circulation (number 2) were determined the most important wishes. The complete order of the comparison can be seen in Table 13.
Table 13. Paired Comparison, with the 5 highest rated highlighted green.
Criteria 2 5 6 9 11 12 13 15 19 20 21 22 24 Sum Sum/Tot
2 - 1 1 1 1 0 1 0,5 1 1 1 1 1 10,5 0,14
5 0 - 1 1 1 0 0,5 0,5 1 1 1 1 1 9 0,12
6 0 0 - 0,5 0,5 0 0 0 1 0,5 0,5 1 1 5 0,06
9 0 0 0,5 - 1 0 0,5 0,5 1 0,5 0,5 0,5 1 6 0,08
11 0 0 0,5 0 - 0 0,5 0,5 1 0,5 1 0,5 0,5 5 0,06
12 1 1 1 1 1 - 1 1 1 1 1 1 1 12 0,15
13 0 0,5 1 0,5 0,5 0 - 0 1 0,5 0,5 0,5 1 6 0,08
15 0,5 0,5 1 0,5 0,5 0 1 - 1 0,5 1 1 1 8,5 0,11
19 0 0 0 0 0 0 0 0 - 0 0 0,5 0,5 1 0,01
20 0 0 0,5 0,5 0,5 0 0,5 0,5 1 - 1 1 1 6,5 0,08
21 0 0 0,5 0,5 0 0 0,5 0 1 0 - 0,5 1 4 0,05
22 0 0 0 0,5 0,5 0 0,5 0 0,5 0 0,5 - 0,5 3 0,04
24 0 0 0 0 0,5 0 0 0 0,5 0 0, 0,5 - 1,5 0,02
Total 78 1
3.6.2 Elimination Matrix
The column regarding the cost ceiling was filled with question marks because the project goal was not to deliver a finished product, but an idea of how it could be solved. With that said, no cost ceiling has been determined for the solution.
Concept 4, 5, 9 and 10 were chosen to be discarded because of the Elimination Matrix.
36
Table 14. Elimination Matrix of the concepts.
Page 1 Elimination matrix for: Drying solution
Elimination criteria:
[+] Yes [-] No
[?] More info needed
[!] Verify requirement specification
Solution Solves the main problem Meets the requirements Feasible Under cost ceiling Safety and ergonomics Fits the company Enough information
Decision:
[+] Pursue solution [-] Eliminate solution [?] Seek more info
[!] Verify requirement specification
Comment Decision
1 + + + ? + + + +
2 + + + ? + + + +
3 + + + ? + + + +
4 ? + - ? + + + Uncertain how to solve the problem of refilling the surfactant, without it becoming too irritating.
-
5 ? + - ? + + - -
6 + + + ? + + + +
7 + - + ? + + + -
8 + + + ? + + + +
9 + ? ? ? + + - This concept is remarkably similar to the existing system, and doubtfully a big difference in
performance.
-
10 + - + ? - + + Dividing the dishing space into two separate spaces is a too severe reconstruction for this project.
-
3.6.3 Pugh Matrix
Most of the wishes and requirements within the Criteria Matrix are dependent on a more detailed solution and therefore hard to determine. By reason of this, most of the wishes and requirements did not allow for an equitable estimation of its comparison to the reference solution. Therefore, were most criterions discarded.
37 The concepts that were determined to be pursued and challenged with SCAMPER were
concept 3, 6 and 8.
Table 15. Pugh Matrix of concepts 1, 2, 3, 6 and 8.
Criteria Alternatives
[ref] 1 2 3 6 8
Req. 1 D
A T U M
+ + + + +
Wish 2 + + + + +
Req 3 0 0 0 0 0
Req. 4 0 0 0 0 0
Wish 5 0 0 0 + +
Wish 12 - + + + +
Wish 13 - - + 0 0
Wish 15 - - 0 0 0
Wish 19 + + + + +
Wish 21 - - - 0 0
Sum [+] 3 4 5 5 5
Sum [0] 3 1 4 4 4
Sum [-] 4 3 1 0 0
Net value 0 -1 1 4 5 5
Ranking 4 5 3 2 1 1
Proceed - no no yes yes yes
3.6.4 SCAMPER
By utilizing the SCAMPER method on concept 3, 6 and 8, two new modifications of sub- solutions were generated. One regarding the convection and the other regarding the runoff.
The runoff solution “the tray” could be modified/solved by it being pulled out like a curtain from the side of the dishwasher. This means that the basket is not present during the washing cycle, hindering the washing results. When the washing cycle is complete, the tray solution is pulled out to prevent the water from dripping down onto the lower basket’s dishware. This result in less water on the dishware in the lower basket. The solution is visualised with a sketch, see Figure 20. This solution can act both as a solution for the runoff itself, or together with the vibration movement to enhance the results of a more even drying process.
38
Figure 20. Sketch showing the tray solution being pulled out.
The other solution that came up during the SCAMPER session was for the convection process.
The idea can be likened with a dryer at the carwash, which sweeps closely over the car, in this case the dishes. An oblong air dryer, see Figure 21, sweeps over the basket by gliding on rails and target each component of the load. This solution could be limited to horizontal movement or utilize both horizontal and vertical movement.
Figure 21. Sketch showing the idea of having an oblong, sweeping, air dryer
3.7 Final Concept Selection
A slightly changed Concept 8, consisting of the tray, reversed airflow and rotation of the dishware was deemed the most reasonable concept to pursue with this project.
The vacuum pump enhancer was determined not to be pursued with this concept. Because vacuum pumps are loud, and the lower pressure inside the dishwasher reduces its structural
39 integrity, which could lead to unexpected problems. To reduce the noise from the pump, a layer of sound isolation must be added, and reinforcement of the surrounding walls to increase its structural integrity. With that taken into consideration, rotating the dishware 90° is
determined to take its place. By rotating the dishware, the plates etc. will be parallel to the air flow, instead of normal to the flow, thus allowing for increased air circulation because the air can easier pass between the dishes, instead of having to go around it.
Figure 22. Visualisation of the air flow with the plates normal to the air flow.
Figure 23. Visualisation of the air flow with the plates parallel to the air flow.
The concept of how the tray solution could be solved was deemed reasonable for this project, with the Elimination- and Pugh matrix as support.
Reversing the airflow compared to making the whole side into an outlet has a greater conceivable impact on the drying process and more suitable for the projects time frame.
The carwash like dryer was discarded after a conversation with the supervisor at ASKO.
Because of two reasons: it is too time-consuming to develop it and blowing the water off instead of using convection means that the air flow must be of such degree that the dishware starts to shake before the water moves.
