Compression/Absorption cycles for large heat pumps - Systems simulations
Licentiatavhandling, 1987

The compression/absorption cycle can, in many situations, give an improved performance compared to the single-fluid compression heat pump. Also other advantages can be achieved such as the possibility to use an already known refrigerant within a new temperature range. From environmental aspects this is important since it offers a possibility to reduce the use of the halogenated hydrocarbons Rll, R12 and Rl14 which are destructive to the ozone layer. In this work three different compression/absorption cycles, using a mixture of ammonia and water, were simulated. From the beginning the three mixtures H2o/LiBr, CH 30H/LiBr and NH3/H2o were considered but since NH3/H2o gave the better performance it was chosen for the further study. The three cycles were chosen with the intention to achieve an improved performance for three different situations: - when the temperature gradients of the heat sink and the heat source are large and of the same magnitude - when the tempe~ature gradient of the heat source is large compared to the gradient of the heat sink - when a large temperature lift is required A comparison between the compression/absorption cycle and a compression cycle working with the optimal refrigerant within each temperature range shows an improvement in COP for the former cycle ranging from 0% to 30%. The specific capacity shows an even larger improvement for the compression/absorption cycle, between 35% and 55%. When considering the compression/absorption cycle in different case studies the greatest improvement is achieved for the industrial cases where the temperature level is high. Also at lower temperature levels there is an improvement for the situations where the temperature gradients of the sink and the source are large.


Lena Åhlby

Institutionen för värmeteknik och maskinlära



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