The Exploitation of Low-Temperature Hot Water Boiler Sources with High-Temperature Heat Pump Integration

Abstract

The article presents an original and innovative technical solution for the exploitation of low-temperature excess heat from hot water boilers that use gas or liquid fuel for the needs of high-temperature heating in buildings or in industry. The primary fuel efficiency used for hot water boilers can be significantly increased by utilizing the excess low-temperature heat of flue gases that are discharged into the environment and thus also reduce CO2 emissions. Hot water systems usually operate at higher temperatures of the heating water, which is transported to the heat consumer via supply pipe, and the cooled heating water is returned to the hot water boiler via the return pipe. For the excess low-temperature heat exploitation of the flue gases from hot water boiler, it is necessary to install a condenser in the flue gas discharge pipe, where condensation of water vapour present in the flue gas heats water or a mixture of water and glycol. The heating water, which is cooled and returned from the heat consumer via the return pipe, is led to the condenser of the high-temperature heat pump, where it is preheated and then led to the hot water boiler, where it is heated to the final temperature. A computer simulation with the Aspen plus software package for the series or parallel connection of high-temperature heat pump to a hot water heating system and the economic analysis of the excess heat exploitation from the flue gases are also performed.

Carbon-Free Heat Production for High-Temperature Heating Systems

“…evaporates and is led to the flash-tank or separator, where the steam and condensate are separated. The vapors are then led to the compressor of the second stage of compression, and the condensate is led via the reduction valve VALVE1 to the evaporator of the first stage, where it is vaporized as a refrigerant with the heat obtained by cooling the lowtemperature heat source [13]. The operation of a two-stage heat pump is shown in the T,s diagram in Figure 3.…”

“…Their use is possible in all industrial fields where low-temperature fluid heat fluxes are generated. Their efficient way of harnessing low-temperature sources to improve specific energy use in processes, increase efficiency, and reduce CO 2 emissions is due to lower fossil fuel consumption [13]. HTHPs are already available commercially in different sizes, forms, operating principles, and types of refrigerants used.…”

Recent Advances in Low-Carbon and Sustainable, Efficient Technology: Strategies and Applications

“…Goricanec et al [180] used Aspen Plus software for exploring low-temperature heat recovery from hot-water boilers. They evaluated the series and parallel connections between the heat pumps and the water-heating system.…”

Investigation of the Concentric Heat Pump with Improved Energy Performance

“…Various schemes for using HP are known. For example, installing an HP condenser in the exhaust pipe of liquid fuel hot water boilers to recover the condensation latent heat of low-temperature water vapour from the flue gases, which also reduces the emissions of СО 2 contained in the flue gases [7]. Other researchers investigated the use of HP to recover waste heat at 45°C to generate steam above 150°C.…”