Novosibirsk State Technical University (NSTU) is exploring the possibilities of using absorption thermal transformers with a working fluid, an aqueous solution of lithium chloride, in heat supply systems and in industry to solve energy—saving and low-potential heat utilization problems.
Absorption thermal transformers (ATT) are highly efficient energy-saving equipment that uses thermal energy for their operation. They can be used in the production of artificial cold at positive temperatures (refrigerating machines) and the transformation of waste heat to a higher temperature level (heat pumps), said Dmitry Mukhin, a graduate student at the Department of Thermal Power Plants at NSTU-NETI.
The ATT of all global manufacturers mainly uses two working pairs: LiBr+H2o and H2o+NH3, each of which has its drawbacks. For a working solution of lithium bromide, this is a high corrosion activity and the risk of crystallization at low temperatures, for an ammonia solution, it is a toxic refrigerant NH3. An important aspect of the research conducted at NSTU-NETI is the search for alternative working couples.
The scientific work was carried out by a postgraduate student under the supervision of Sergey Lvovich Elistratov, Doctor of Technical Sciences, Associate Professor of the Department of Thermal Power Plants. It was proposed to use a LiCl + H2o pair as an alternative working pair for absorption bromistolite refrigerating machines (ABRM) and absorption bromistolite heat pumps (ABHP). Absorbent is an aqueous solution of lithium chloride, compared with a solution of lithium bromide, has less corrosion activity and lower cost. The task was to compare the energy efficiency of ATT for two working bodies: LiBr+ H2o and LiCl+H2o.
At the first stage of the work, comparative theoretical studies were carried out: calculation of the ABRM and ABHP cycle for LiBr and LiCl absorbers and determination of energy efficiency values for industrial and thermal energy use parameters. The energy efficiency indicators are the thermal coefficient for the refrigerating machine and the transformation coefficient for the heat pump.
The calculations performed by the scientists have shown that the values of thermal coefficients and transformation coefficients for ABTT and AHTT are comparable. This opens up the prospect of using absorption chlorolithium thermal transformers instead of absorption bromistolithium thermal transformers in certain temperature ranges, in particular, for the use of heat pumps with water heating in autonomous heat supply and hot water supply systems and for heating the environment in industry (partial heat recycling in production, where heat of low temperature potential from 40 ° C to 90 ° C is transformed high-potential heat with temperatures from 55 °C to 120 °C).
"Currently, the most promising direction is the use of absorption chloride lithium thermal transformers in autonomous heat supply systems in remote areas of Russia, where there are geothermal sources with temperatures of about 40 ... 45 ° C. Such temperatures are insufficient for autonomous heating and hot water supply systems. The problem of heat supply can be solved by using a boost-type AHTT. For example, there is a geothermal source with a temperature from 40 °C to 45 °C. In winter, water can be heated to temperatures from 55 to 63 ° C with the help of a boost-type AHTT, which is sufficient for heating and hot water supply. At the same time, the cost of electricity for such production will amount to no more than 40 kWh for each gigacalory of heat. To remove heat from the condenser, ambient cold air is used with a temperature sufficient to maintain a condensation temperature of 4 ° C," Dmitry Mukhin said about the application scenario of the AHTT.
In the future, it is planned to develop, manufacture and install a stand simulating the operation of ABTT and AHTT, to conduct comparative experimental studies of energy efficiency indicators for the two working bodies. In case of successful tests, it is planned to create a pilot industrial model of the AHTT.