Heat recovery systems

In refrigeration systems, heat taken from the refrigerated body and received in the compressor during the compression process is given to the surrounding environment. During the adiabatic compression process, internal energy of the vapour increases by the quantity of heat which equals to the work performed during compression. Refrigerator vapour, which is forced to move into the condenser, is always in the state of superheating and of high temperature. Vapour is cooled down until the start of the condensation in the pipeline to the condenser and to the upper part of the condenser, and the subsequent heat transfer to the environment causes the vapour condense and turn into a liquid at a constant condensing pressure. The compression temperature depends on the refrigerant, boiling and condensation temperatures and compressor type (positive displacement, rotary screw etc). In order to recover the heat transferred to the environment, one has to use the intermediate fluids, usually water. Since, depending on the size of the system, the quantities of the condensation heat are indeed appreciable, the recovered heat is quite a significant contribution to the overall energy savings. The trouble is that all taken condensation heat is of relatively low, +35 °C, temperature, while the condensation temperature is at +40 °C. The water heated to this temperature or certain antifreeze liquid may be used for floor heating, ramp or path protection from ice during the winter time as well as for primary water heating or for technical purposes.

Knowing that the vapour compression temperature ranges from +70 °C to +110 °C (depending on the aforementioned conditions), systems with partial heat recovery of the superheated vapour are designed — heat is removed from the vapour to the beginning of the condensation state. In this case, water can be heated up to +60 °C…+65 °C.