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The purpose of this work is development of the heat transfer calculation method of a water low-temperature ceiling capillary heating system for heating rectangular rooms. Recently, such systems have become widespread due to their advantages over traditional heating devices: the use of a coolant with a low temperature potential, high heating speed rate of the internal air, low temperature gradient in the height of the room, absence of noticeable air masses movement and dust flows, ability to work in cooling mode. However, such systems are still incompletely studied, and constructive calculations or calculations of thermal and hydraulic modes are carried out according to formulas obtained empirically, thus, calculations do not always have high accuracy. The paper proposes a heat transfer process calculation method from the considered low-temperature heating system, which allows determination of the heat flow value with high accuracy. It`s revealed that in the considered configuration of the system location (on the ceiling), a significant proportion of heat transfer is infrared radiation, and the convective component is very small. Therefore, it was very important to accurately describe the radiant heat exchange by mathematical equations. The calculation of the radiant component of heat transfer was carried out with the theory of radiation view factors. Experimental test of the studying object was carried out to find the missing values, as well as to verify the results obtained using the proposed calculation method. The calculation results had a slight deviation from the results obtained experimentally (the error was 6 %).

Heat losses in industrial processes can be divided into three sections (high-, medium-, and low-temperature heat), depending on the temperature of the exhaust gases. This heat is usually recovered either by heat exchangers or by a closed Rankine cycle. However, about 60% of low-temperature heat losses remain irreplaceable. Currently, the organic Rankine cycle has become a promising method of low-temperature energy recovery, and several theoretical studies on this topic have appeared, but a small number of experimental studies have been performed. In our work, we have built a 2 kW heat recovery laboratory test bench using tube-type heat exchangers, a gear pump and a turbo expander on the working fluid R141b. As a result, we found that the efficiency of the cycle increases as the boiling point and pressure increase, but an increase in overheating at the inlet of the expander leads to a decrease in efficiency due to the use of the working fluid R141b. At the inlet of the evaporator and the outlet of the condenser, respectively, overheating and supercooling of the working fluid occurs, which negatively affects the efficiency of the cycle. The amount of useful heat obtained was 45.4 W with an efficiency of 2.24%. as a result of low efficiency of the expander and pump, as well as leaks during the test. The development of an experimental test bench with working on organic Rankin cycle requires long-term research work and great scientific potential. In the future, it will be necessary to create a new test bench based on a deeper study, so that we can get a higher efficiency of the expander and pump, which would affect the efficiency of this cycle. Also, we need to replace the working fluid in the cycle with a more efficient one.

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