| 摘要 |
Heat pumps serve to extract thermal energy from the air and from flowing water or groundwater. In practice, this is a reversal of the known refrigerator principle. The range of application of air/water heat pumps is small, in practice only 38% of the heat required can be extracted from the air, because the efficiency is adequate only within a small temperature range. However, 62% of the thermal energy is required in the range from -20 DEG to +2 DEG , and given a possible efficiency of epsilon = 1.66 there is no longer any advantage. The reasons are to be sought essentially in that the pressure relationships in the compressor assume unfavourable values, while in the case of multistage compression more favourable values arise, as can also be seen from the known energy p-h diagrams. Again, in the case of multistage compression the stage losses can be resupplied to the circulation process and, in addition, individual stages can - as a function of temperature - be connected or disconnected, thus enabling a higher efficiency.
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