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In the case when there is a difference in consumption on the side of the cold and hot heat carriers, the use of channels with the same corrugation height in one heat exchanger leads to a decrease in velocity of the heat carrier on the side with low consumption. Low velocity contributes to appearance of deposits on the heat transfer surface, which leads to disruption of operation mode of the apparatus and a forced clean-up stop. In case of using channels with a different corrugation height (cross-section area), velocities in the channels are aligned and intensity of emergence and growth of contamination falls sharply. It also allows us to reduce the heat transfer surface area of the apparatus and fully implement permissible pressure losses on the sides of the heat exchanger. For designing of heat exchangers of this structure, the authors developed the mathematical model that allows making calculations of heat exchangers for assigned operation conditions with the use of geometrical data of the plates, thermophysical properties of heat carriers and criterial equations for plates of the selected type. The calculation algorithm involves determining of the ratio between corrugation heights. Practical value lies in the fact that the proposed approach makes it possible to extend the service life of the heat exchanger prior to a maintenance stop. This enables provision of continuity of the technological process and decreases operation costs. Calculation of the heat exchanger of hot water supply by the parallel scheme of attachment to heating networks and the heat exchanger of stage 1 of the two-stage hybrid scheme was presented. Calculation data indicate a decrease in the heat transfer surface area compared to heat exchangers with channels of equal height, full realization of pressure losses and their alignment in the channels, which facilitates an increase in resistance to contamination of the plates’ surface. Calculation showed the advantage of using apparatuses with channels of different cross-section area. The higher the ratio between consumption of heat carriers in the channels, the stronger this advantage.

The problem of modernization of the heat module with two-stage mixing scheme connection of hot water supply by installations of the heat pump during interheating period is considered. Heating water of the in-house circuit of the building heating system is used as a heat source for heat pump. The district cooling of the residential areas is possible through the heaters during the summer. R600 refrigerant is chosen for heat pump for its environmental-friendliness and low-pressure of evaporation and condensation. The economic calculation is made for interheating period comparing the operation with and without heat pump. This paper advances selection of optimum amount of heat to be recovered during low potential heat utilisation and targets for heating and cooling capacities.

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