On the development of high temperature ammonia–water hybrid absorption–compression heat pumps

Abstract

Ammonia-water hybrid absorption-compression heat pumps (HACHP) are a promising technology for development of efficient high temperature industrial heat pumps. Using 28 bar components HACHPs up to 100• C are commercially available. Components developed for 50 bar and 140 bar show that these pressure limits may be possible to exceed if needed for actual applications. Feasible heat supply temperatures using these component limits are investigated. A feasible solution is defined as one that satisfies constraints on the COP, low and high pressure, compressor discharge temperature, vapour water content and volumetric heat capacity. The ammonia mass fraction and the liquid circulation ratio both influence these constraining parameters. The paper investigates feasible combinations of these parameters through the use of a numerical model. 28 bar components allow temperatures up to 111

Analysis of temperature glide matching of heat pumps with zeotropic working fluid mixtures for different temperature glides

“…If in these cases the temperature glide match could be improved by any cycle adjustment while retaining the fluid and the remaining components constant, the exergy destruction in the component and thus, in the entire system would decrease and improve the performance. Possible cycle adjustments are extensively discussed for water ammonia systems [35].…”

Design of serially connected district heating heat pumps utilising a geothermal heat source

“…As shown in both [22] and [19] the choice of x r and f affect both the system performance (COP) and the system investment. The optimum values of x r and f depend on the HP operating conditions such as sink/source temperature differences as well as the temperature lift [22].…”

“…The reduction of vapour pressure is an advantage for high temperature applications, such as district heating, as it allows the utilisation of low pressure component for high temperature applications [18]. With the current pressure level of commercially available components the HACHP is capable of delivering significantly higher temperatures than the conventional vapour compression heat pump (VCHP), however this requires the correct combination of ammonia mass fraction and circulation ratio to be identified [19]. The HACHP has been shown to provide a good return on investment as well as a significant reduction of CO 2 emission when applied for industrial process heating, in e.g spray drying facilities [20].…”

Numerical study of a hybrid absorption-compression high temperature heat pump for industrial waste heat recovery

“…Kim et al [11] experimentally tested a 10 kW HAC-HP system using ammonia-water as working fluid, and elevated the heat from 50 °C to over 90 °C with ammonia mass fraction in the weak solution of 0.42. Jensen et al [12] numerically investigated the influences of ammonia mass fraction and liquid circulation ratio on the system constrains, results showed that the maximum heat supply temperature was 111 °C when using standard refrigeration components without modifying the compressor (28 bar limitation); for high pressure ammonia based components, the maximum supply temperature can be 129 °C (50 bar limitation) and for transcritical CO2 based components, the maximum supply temperature can be 147 °C (140 bar limitation). The authors [13] i.e.…”