Technical and economic working domains of industrial heat pumps: Part 2 – Ammonia-water hybrid absorption-compression heat pumps

Abstract

The ammonia-water hybrid absorption-compression heat pump (HACHP) has been proposed as a relevant technology for industrial heat supply, especially for high sink temperatures and high temperature glides in the sink and source. This is due to the reduced vapour pressure and the non-isothermal phase change of the zeotropic mixture, ammonia-water. To evaluate to which extent these advantages can be translated into feasible heat pump solutions, the working domain of the HACHP is investigated based on technical and economic constraints. The HACHP working domain is compared to that of the best available vapour compression heat pump with natural working fluids. This shows that the HACHP increases the temperature lifts and heat supply temperatures that are feasible to produce with a heat pump. The HACHP is shown to be capable of delivering heat supply temperatures as high as 150 ○ C and temperature lifts up to 60 K, all with economical benefits for the investor.

Technical and economic working domains of industrial heat pumps: Part 1 – Single stage vapour compression heat pumps

“…One HFC working fluid (R134a) is included in the study for comparison of the feasibility of natural working fluids. The considered sink temperature range is from 40 C to 140 C. In part 2 of this paper (Jensen et al, 2014), the ammonia-water absorption-compression heat pump is studied and compared to the results of the VCHP determined in this paper.…”

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]. Further, x r and f influence the technical constraints such as high pressure, p H , and compressor discharge temperature, T H .…”

“…The thermodynamic, heat transfer and economic models of the HACHP were implemented in Engineering Equation Solver (EES) [28] and follows the procedure presented in Jensen et al [22]. The inputs to the thermodynamic model may be seen in Table 2.…”

“…For the analysis, the limitation was confined to be below 180 • C, but other suppliers may require further reduction. For the HACHP technology, this technical limit is a significant obstacle in order to achieve high sink temperatures [22]. Based on the derived results of Section 3.2, the relation of optimal mass flow ratio was determined for a range of heat load ratios between 0.2 and 0.6.…”

“…Detailed thermodynamic and economic models of various single stage VCHP and HACHP were developed and investigated in Ommen et al [21] and Jensen et al [22]. The results show, that the best available technology in terms of net present value (NPV), typically depends on the performance and investment of the HP systems at the specific layout of the sink/source process streams.…”