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Development of an expansion valve to reduce energy consumption of cold vending machines and small commercial refrigeration systems

Final Report Summary - EXPAND (Development of an expansion valve to reduce energy consumption of cold vending machines and small commercial refrigeration systems)

Executive Summary:
The Expand consortium has developed a low capacity expansion device for HC and CO2 refrigerants together with a control system that enables efficient modulation of refrigeration system capacity in relation to load. This has enabled cumulative energy consumption savings of 20% for a refrigerated vending machine, thereby enabling the European vending industry to regain a technological edge. The Expand valve is easy to manufacture using conventional manufacturing techniques and can therefore be made cost effectively in relatively small production volumes.
At the initial phase of the project a search on commercially available expansion devices and concepts was performed in parallel with a market analysis. This study confirmed the market need for the Expand low capacity expansion device Pulsating refrigerant flow was analysed on its heat transfer behaviour on the evaporator. Based on theoretical models and practical measurements, it has been concluded that pulsating flow generally does not negatively affect the overall heat transfer of an evaporator and that therefore pulsating flow can be applied for an expansion device. Another theoretical model was developed to study the dynamic behaviour of a given expansion device design for a range of operating conditions. Input parameters were the geometry, the materials applied and the refrigerant used. The model calculates inertia, damping and stiffness, which finally results to the required actuation force and, if applicable, the spring stiffness.
Five commercial refrigerated cabinets with a capillary operating on CO2 or HC were tested on their performance at different ambient conditions during normal steady state and dynamic cooling down operation. It was concluded that in general evaporators are not optimally filled and that energy efficiency improvements of 8 to 20% should be feasible by improving the evaporator filling at the initial start of the (relatively short) compressor on phase and by avoiding refrigerant migration to the evaporator during the compressor off phase.
Nine design concepts for new low cost expansion valve technologies were generated. Some of these have been modelled in a 3D CAD to provide a simpler explanation of their functionality. For three of the designs transparent models were produced for better understanding of these concepts. Initially, three fully operational brass prototype valves with integrated solenoid coil were manufactured. The coil of these models needed to be assembled to the valve with a winding machine which was specifically designed and manufactured for this purpose. Further investigation resulted in an improved new design, for which “off the shelve coils” could be applied. It is obvious that such a concept is more practical and cost effective. The concept was further developed and improved. The final valve can be manufactured from just 10 components using low cost conventional manufacturing techniques which do not require major investments in production and tooling. Once manufactured it can be assembled in less than 1 minute. A dedicated controller was also developed which includes a thermostatic bypass module enabling the delay of compressor on time to ensure the ideal quantity of refrigerant is present at the inlet of the expansion valve at the start-up of its operating cycle.
The final concept (including control) was integrated in a refrigerated vending machine, a beverage cooler and a commercial chest freezer. Tests in climate rooms showed that for the beverage cooler and the freezer marginal energy savings (5% max) were found. However for the vending machine an energy saving up to more than 20% was achieved, which is in line with the initial target of the project and very substantial. At the end of the project a seven weeks field test was performed with each of these three appliances. During these tests no substantial failures were noted; the reliability and the robustness of the valve and controller were validated as satisfactory.
Project Context and Objectives:
The European Vending Association (EVA) is composed of 20 national associations, who represent Europe's SME industry of machine and component manufacturers, suppliers of commodities (ingredients, confectionery, soft drinks) and operators. Our chilled vending sector is heavily based on older HFC refrigerant technology. In contrast Japan has embraced natural refrigerants and is the leading manufacturer of CO2 and Hydrocarbon (HC) vending machines. As a result, our industry needs to innovate and develop advanced components and systems, to remain competitive and provide cost effective, energy efficient products. Small refrigeration systems as used in vending machines use capillaries as the expansion device, however they do not enable optimal operation over the range of refrigeration loads. Away from design point load, coefficient of performance drops due to sub-optimal filling of the evaporator. More advanced control systems may be introduced by replacing the capillary with an expansion valve, however for refrigeration systems in the 50-750W capacity range these are challenging to manufacture cost effectively, due to small orifice sizes. In response, the Expand consortium has developed a low capacity expansion device for HC and CO2 refrigerants together with a control system that enables efficient modulation of refrigeration system capacity in relation to load.
To develop such an expansion device the following objectives of the specific work packages are relevant:
WP 1: Completion of preparatory research, modelling and simulation tasks. The objective of this work package is to derive conceptual design(s) for the Low Capacity Expansion Device (LCED). To derive these designs the, the influence of the design on the performance of the cooling system, the activation forces required and the power consumption resulting must be quantified. To analyse the influence of the design on cooling system performance, mathematical models describing the influence of expansion device design on the entropy change of the refrigerant have been developed and validated using practical tests. To quantify the activation forces and the power consumption of the designs, mathematical models describing the dynamical response of the expansion device and the interaction with the fluid will have been set up.
WP2 Determination of performance specifications. The objective of this work package is to create a list with required response times and control parameters for an expansion device operating on Hydrocarbon, CO2 and Hydrofluorocarbon refrigerants, resulting in a 10% energy saving for the current small capacity commercial plug in coolers placed on the European market and for future products to be placed on that market.
WP3 Electrical and mechanical design of expansion devices and its control: The objective of this work package is to design an expansion device for Hydrocarbon, CO2 and Hydrofluorocarbon refrigerants, hardware prototypes with control included, through iterative testing and development design cycle.
WP4 Prototype assembly and optimisation. The objective of this work packages is to assemble and design prototype production samples, including the integration of the control system, in order to comply with the specification.
WP5 Infield trials and validation. The objective of this work package is to validate the energy consumption reduction and gain feedback from service engineers and well as the market
WP6: Exploitation, dissemination and training. The objective of this work package is to:
1) Transfer knowledge from RTD partners to SME-AG partners and from SME-AG partners to SME consortium.
2) Train of EVA membership in the benefits and application of the Expand LCED device and control system
3) Protect of IPR related to the project for the benefit of the members of EVA
4) Develop commercialization and future funding strategy
WP7 Management. The objective of this work package is to:
1) manage the project budget including distribution of money to partners and cost claims
2) Manage the consortium agreement and other contractual arrangements relating to the project
3) Manage technical deliverables and associated reporting procedures
4) Ensure the project remains on-time and within budget

Project Results:
Result 1: Five scientific models to be used during the development phases
1) To analyse the design of a given expansion device and to qualify the differences in expansion efficiency of various expansion devices, a calculation model has been set-up. This calculation model is based on using elementary elements (orifice, capillary tube connection node) that can be combined to create a final model describing the behaviour of an expansion device design. The model calculates the refrigerant mass flow and the change in fluid properties (pressure (P), Temperature (T),vapour fraction (x), Enthalpy (H) and Entropy (S) ) of the fluid through the device based on given inlet properties (fluid type, fluid pressure (P), fluid temperature (T), vapour fraction (x)) and outlet pressure (P).
2) To analyse unsteady flow effect on the cooling system performance, a theoretical model has been made based on quasi static approach and applying heat transfer correlations for two phase steady flow. This model predicts that the difference between steady and pulsating flow is marginal (max 1%).
3) To analyse the pressure drop of the refrigerant flow, pulsating flow was modelled and measured to be 1.5 times higher compared to steady flow. This pressure increase is significant and has to be considered when pulsation is present. The goal of the task was to define the influence of pulsation on the heat exchange and pressure drop. It was found that for a typical refrigerant to air evaporators the total heat exchange for pulsating flow is similar to steady flow.
4) To analyse the dynamic behaviour of the moving body of the expansion device a numerical model was created, solving the non-linear equation of motion. With this model, the dynamic behaviour of a given expansion device design can be studied and optimised for a range of operating conditions.
5) An existing cold appliance simulation model was modified to include the functionality of the low capacity expansion device under development.
Result 2: Practical verification of potential energy savings of an expansion device
Five commercial cabinets selected were purchased and subsequently tested in climate rooms. Steady state and dynamic tests were performed at different environmental temperatures. The test results confirmed the assumption that the evaporator is not optimally filled and that energy savings are feasible. A high precision controlled expansion device was developed with real time feedback and with measurement equipment included. Experimental validations with this test set-up, showed a 12 and 20% reduction in cooling system energy consumption for respectively a CO2 and a R-404A based cooling system of a vending machine when applying an automatic expansion valve with closing valve functionality in comparison to the benchmark capillary based system. Analyses showed that 50 to 70% of this gain can be contributed to improving the cyclic average evaporator filling and that the remaining gain is resulting from avoiding refrigerant migration through applying closing valve functionality. Based on practical results, supported by simulation data using the simulation model, estimations have been made about the expansion device energy saving potential for each appliance category within scope. From this it is shown that, except for commercial chest freezers, all appliance types show a significant efficiency gain of more than 8%.

Result 3: Final Prototypes
As a result of many design iterations resulting in improvements, 20 final prototype samples have been produced, of which 15 have been assembled into demonstration kits for project partner evaluations and as dissemination support for EVA members. The final prototype samples have been successfully integrated with the control system and tested on flow tests, leakages, controller functionality, closing functionality and burst. The explosion safety of the valve and controller is satisfactory provided that the control board and the thermostat delay board are built into a hermetically sealed plastic box. Results 4: Energy implementation of the valve in cooling appliances
To ensure proper operation with the valve, three cooling appliances were equipped with the valve and tested in laboratory and field conditions. The main goal of the laboratory tests was to validate the impact on appliance energy consumption of using the valve in comparison to the original capillary tube. Based on earlier learnings, the largest energy consumption reduction was expected for the vending machine (around 12 to 20%). The actual results of the measurements were in line with the expected energy consumption reduction. For the chest freezer and bottle cooler the actual savings measured are marginal (max. 5%), while for the vending machine savings of more than 20% were measured. In addition to the steady state energy consumption measurements, a half reload recovery test was performed on the bottle cooler. This resulted in a 10% reduction in cooling down time. After running the appliances for more than 6 weeks in the field, no failures were noted; therefore the reliability and robustness of the valve and controller are validated as being satisfactory and will provide a very sound foundation for post project commercialization work
Result 4: User Guide and Installation manual
The Expand project user guide and installation manual contains the appropriate level of user instruction to implement the final designs and prototypes. The instructions of the developed prototypes related to the technical design, assembly, installation and service. The estimated energy savings possible are also presented. The guide has been prepared as a 28 page booklet, which is available in both electronic form and as hard copies.

Potential Impact:
In Europe R134a and R404A refrigerants are still applied in commercial cold cabinets and refrigerated vending machines, but this market is moving towards natural refrigerants such a HC and CO2. The trend is initiated by multinational companies like Coca Cola, Unilever and Heineken who have decided (policy wise) to purchase fridges with natural refrigerants only. Another driver is the European Fluorinated Gas Regulation, which prohibits R404A in 2020 and R134a in 2022. This means that from 2022 commercial cold cabinets with HC and CO2 refrigerants will dominate the European market.
With respect to the energy use of these appliances, regulation is expected to be implemented in Europe early 2018. Maximum energy use limits will be defined (Eco-design) and an energy labelling scheme (similar to the current scheme for domestic refrigerators) will be introduced. It is evident that expected energy savings of more than 20% will be considered as an interesting option to improve the energy efficiency label, which is of course of commercial interest. Note that yearly 1.3 million commercial cooling appliances are placed on the European market for which the expansion device can be applied. This number is expected to grow to 1.7 million in 2025.
The partners have prepared 5 project videos and a conference article which will all help to broadcast the project results to relevant target stakeholder groups. In addition project information was distributed via the project partner websites and social media.
Research results, low cost expansion device, control system hardware, control system firmware and the integrated Expand system were delivered within the project. Initially, it was considered that any number or combination of these results could be filed for Intellectual Property Rights (IPR). However, as the purpose of the project results is not to financially benefit the EVA (as a non-profit organisation), the EVA and project partners have decided that the project results should not be protected by IPR. The EVA believes that the widest uptake of project results cannot be achieved further by applying for IPR protected elements of the project. However, project results will still be protected by the EVA by way of restricting the project information to EVA members through its Members–only website. The EVA manufacturer members will be able to review and use the research and results in their R&D departments.
A dissemination plan was determined and implemented in order to spread awareness of the project and its objectives and to disseminate technical information to the industry and EVA Members.
Meetings were organised with the two largest refrigerated vending machine manufacturers in Europe SandenVendo and Sielaff in order to disseminate the project and to achieve feedback to define the expansion device specifications. In addition the project introduced and updated at EVA technical committee meetings in Brussels, as well as the publication of multiple online articles on the project. A publically accessible website was also produced and updated every 3 months, and a specific section on the EVA Members only website was created to act as a knowledge base for members.
Presentation of more technical dissemination began with Re/genT presentations and progress reports at EVA technical Committees. The project exhibited at Venditalia 2015 with a dedicated booth, in order to present Expand to the wider vending industry. Venditalia is the largest worldwide vending exhibition with 20,000 visitors and so was ideal to present directions and prototypes to relevant manufacturers. The first of 4 project videos was created and disseminated in Stage 2, as well as an intensification of EVA project marketing of Expand articles to industry publications and promotion online.
Knowledge transfer took place between Expand RTD partners Re/gent, NWI, Inray and the EVA technical committee and other Expand SME partners, in order to ensure that the relevant EVA Members have sufficient knowledge of the project results are to be in a position to consider manufacturing/purchasing possibilities.
Training and educational materials were prepared and disseminated during Stage 3, including a presentational kit box of the expansion device, controller, as well as a user guide.
Two further animation videos were produced, in order to complement the project results and assembly guide, and a professional project video was produced and published explaining and promoting the project more in depth.
A project update was also presented to the entire vending industry at Venditalia 2016, and the EVA Annual event for the industry – EVEX.
The EVA intends to issue licenses to manufacturers in order to produce the developed valve. EVA Members and Expand partners will be in a position to initially request the licence. Licence conditions will include a confidentially clause, to ensure as far as reasonably possible that the project results are not immediately distributed to non-European countries.
A benefit of EVA membership is to be in a position to request the licence. As EVA membership includes the largest chilled vending manufacturers in Europe, it is considered that this is the best way to ensure the industry can manufacture and put in use the valve. While EVA members can have free access to detailed project development information and the user guide, in order to receive the files for actually producing the valve, a manufacturer will be required to apply for a licence and commit to confidentiality agreements.
Income could however be generated by selling a licence to non EVA Members who wish to produce the valve.

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