Energy efficiency of circulating pumps when using non-freezing heat transfer fluids

Abstract

Introduction. The article considers the issues of operation of circulating pumps of autonomous heat supply systems when the heating circuit is filled with antifreezing coolants. It is possible to remotely start up a heating system cooled down to –15 °С. Ethylene glycol and propylene glycol antifreeze have been studied as antifreeze carriers. Flow-rate characteristics, power efficiency coefficients are studied for “wet rotor” circulation pumps in versions of electric motors of asynchronous type with constant rotor speed and energy-saving pumps on permanent magnets.
 Materials and methods. The research was carried out on test stands. Wall-mounted gas boilers and electric boilers witha rated capacity up to 24 kW were used as heat generators. Circulation motors, control hydraulic valves, part of the pipes with a length of 6 meters were located in a separate freezer. The pumps and parts of the heating circuit were kept at subzero temperatures for 2 hours before the system was started up
 Results. Pressure and flow characteristics of two types of pumps, energy efficiency coefficients were obtained, comparisons with water coolant are provided, the influence of electric network voltage on the investigated parameters was determined.
 Conclusions. The research has shown the possibility of starting circulating pumps in a refrigerated condition with a temperature of –15 °С. Remote start of the cooled heating system with circulation circuit filling with antifreeze when using hydrocarbon fuel boilers is not possible. Operation of heating systems with non-freezing coolants in the operation temperature ranges of 20–80 °C requires changing in settings of the combustion process and a significant increase inthe circulation pump head in comparison with the coolant water.