Use of low - temperature heat to produce deeper temperature refrigeration by means of a new type absorption refrigeration plant

Project Information

Grant agreement ID: JOE3950004

Project closed

Start date 1 January 1996

End date 30 June 1998

Funded under

• Specific programme for research and technological development, including demonstration in the field of non-nuclear energy, 1994-1998

Total cost

No data

EU contribution

No data

Coordinated by

VEREIN ZUR FOERDERUNG DES TECHNOLOGIETRANSFERS AN DER HOCHSCHULE BREMERHAVEN E.V.
Germany

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Exploitable results

Use of low-temperature heat to produce deeper temperature refrigeration by means of a new type of absorption plant; LOTARP

The objective of the project was to develop an absorption refrigeration plant for the use of low-temperature heat for cold production. According to the results available this objective has been fulfilled. By using an additional absorber/evaporator lower desorber temperatures can be set whereby the temperature of the heat supply can be reduced. Thus it is possible to bring into play waste heat with very low temperatures for the production of cold. The results can be summarised as follows: -Waste heat at 65 degrees Celsius to 60 degrees Celsius (initial and reflux temperatures) can be used for the production of cold at 3 degrees Celsius, even if the cooling water temperatures lie in the range of 30 degrees Celsius to 35 degrees Celsius (condensation temperature about 38 degrees Celsius). The COP value is about 0.34. This value is perfectly acceptable for practical purposes since waste heat is frequently available in sufficient quantities. -Following the start-up phase, the plant's operation is stable. Smaller fluctuations, e.g. in the temperature of the heat supplied, scarcely have any notable influence on the plant's operation. -The plant can run automatically with the aid to the software developed for it. Target values can be changed and adjusted during operation. Direct evaluations of the results are immediately possible. -The process can be simulated by means of the models specially developed for this purpose. The results of the process simulation provide valuable information for the configuration of the controllers whereby mostly level controllers are used. The start-up times are dependent on the filling volume of the individual apparatus. In the case of apparatus based on the spray film principle such as condenser, high-pressure and low-pressure absorber, then changing the guide parameter leads to a relatively significant change in other parameters (e.g. mass flow) since the filling volume is small. In the case of submerged apparatus however, any change that takes place is relatively sluggish. This means that in the case of larger fluctuations (e.g. when there is a major change in the temperature of the waste heat) apparatus with a larger filling volume and in the case of smaller fluctuations apparatus with a smaller filling volume should be used. -The concentration width should not be adjusted abruptly to the conditions demanded but rather very gently. -The measurement and control methods can be simplified to a considerable degree. Simple mechanical swimmer regulators can be used for controlling levels as are found in other refrigeration plants. It is important that the pressure in the rectification column is kept constant e.g. via the mass flow of the cooling water. The downstream values then adjust themselves automatically. -If the heating temperature rises periodically to higher values, e.g. to 90 degrees Celsius, then there is also the possibility to operate the plant in one stage mode, by-passing the absorber/evaporator. In this case the COP value can be almost doubled (on the scale of 0.6 - 0.7).