Plastics for expressor technology (PLET)

Køle- og Varmepumpeteknik

The project is based on a new idea enabling the use of plastic in an expansion engine to utilise the expansion energy in refrigeration plants. 10-20% of the consumed energy in refrigeration can be saved by using the expansion energy. The use of plastic will lower investment costs facilitating widespread use resulting in large savings.

Project description

The project aims to clarify the potential to reduce production costs for a new design of a combined expander and compressor (a so called “expressor”). Expanders produce energy by replacing a throttle valve in the refrigeration plant. The expressor is based on a novel idea and the research will, by the use of rapid prototyping, investigate how plastic can be utilised in the design that requires the rotating part to be flexible. Contrary to known constructions, liquid in the return line from evaporators to the compressor part is not a problem. This opens the possibility to use liquid over feed of the evaporators and thereby save energy by raising the saturated suction temperature. The potential for use of the expressor is particular high for CO₂ refrigeration systems and the focus is primarily aimed at supermarket refrigeration in the range of 20 to 100 kW. Verification of the design is performed at temperatures and pressures representing an application envelope dependent on the plastic materials economically available. A total efficiency of the expressor of 35 % will, depending on the outdoor temperature, result in an improvement of the system COP from 10% to 20% and 20% to 35% if the contribution of the liquid over feed of the evaporators is included. As CO₂ in Denmark is dominating the market for new supermarket refrigeration systems and the number of applications abroad are increasing, the potential for energy savings is very high.

Results

The primary idea of the project is to develop a flexible rotor made of plastic, which – built into a pressure tight housing – will be able to replace the expansion valve in a refrigeration system. The construction works as a combination of an expander and a compressor - hence the term ‘expressor’. Instead of achieving a loss when the pressure is lowered in the ex-pansion valve, useful energy can be harvested, which will increase the efficiency of the refrigeration system.

The design of the rotor has been investigated defined by:

Functional requirements
The pressure enclosure (housing design)
Technologies available for ‘rapid prototyping’ in plastic.

In this project, approx. half of the planned work packages have been carried out, and it was necessary to close the project without meeting the objectives and achieving the de-sired goals.

This is mainly due to the challenges associated with converting the functional idea into a geometric design for ‘rapid prototyping’ in plastic as well as the challenges associated with achieving a high enough quality of the printed element.

Since it is still a wish to protect the idea, this report briefly describes the background of the project and the challenges of solving the task. It does not describe the actual construc-tion.

Key figures

Period:

2015 - 2019

Funding year:

2015

Own financial contribution:

1.26 mio. DKK

Grant:

0.90 mio. DKK

Funding rate:

42 %

Project budget:

2.16 mio. DKK

Participants

Teknologisk Institut (Main Responsible)

Partners and economy

Partner	Subsidy	Auto financing
ADVANSOR A/S
Danfoss A/S
SUPER KØL A/S

Contact

Kontakperson

Christian Heerup

Contact email

chp@teknologisk.dk

Plastics for expressor technology (PLET)

Key figures

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Participants

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