Summary and conclusions

Udvikling af demonstrations- og modulopbygget vandkøleaggregat med NH3 som kølemiddel

This project report describes design and test of a prototype chiller unit with NH₃ as refrigerant.

A module installation will be used as a starting point, e.g. a 200-400-600 kW installation built with/for heat recovery, which should be applicable both as water/water with separate water cooler and with integrated dry cooler, for outdoor placing.

We are aiming at the highest possible COP-value. The selection of a compact installation of very small physical dimensions will be taken into consideration, as will dry expansion / flooded system.

Furthermore the installation must have a need for maintenance which does not differ much from what is known from the HFC-installations. This will require an automatic oil handling and return system from the low pressure side of the installation, which is specifically suited for the problems which are common in connection with use of oil in ammonia installations.

During the course of the project, a number of system solutions were analysed and at the end of the project a prototype was built and tested.

The tests carried out on the unit show that the COP is 3.4-4.0, which is not immediately satisfactory. However, considering the fact that the chiller unit is a prototype which will be optimised at a later stage, the result obtained now is relatively reasonable.

Proposal for improvements:

Improvement of the condenser in order to obtain a lower discharge temperature
Evaporator with bigger surface (higher suction temperature)
Usage of frequency converter for capacity regulation

Summary of project result:

With this project we have succeeded in constructing a prototype with NH₃ as refrigerant, which – if the commercial conditions (cheaper components) are present – can be mass-produced subsequent to certain technical adjustments.

The developed oil handling and return system has the intended effect, which implies that we have reached our goal regarding the required maintenance which is comparable to the requirement known from the HFC installations.