Cycle optimization and environmental economic evaluation of transcritical CO₂ heat pump heating systems

doi:10.3969/j.issn.2097-0706.2026.04.009

Abstract

Abstract:

As a representative of clean heating， air-source heat pumps can effectively reduce building energy consumption， but their application in cold regions faces technical bottlenecks， and traditional refrigerants have negative impacts on the environment. Therefore， taking the transcritical CO₂ heat pump heating system as the research object， the system performance was simulated and analyzed based on Dymola software. The heating performance of CO₂ single-stage cycle， two-stage cycle and two-stage cycle coupled with mechanical subcooling under different operating conditions was compared and studied. Combined with the annual actual heat supply， environmental analysis and economic evaluation of the system were conducted， and the applicability and sustainability of different system forms were comprehensively discussed. The research results showed that the heating coefficient of performance（COP） of the two-stage cycle was increased by 26% compared with the single-stage cycle. The transcritical CO₂ one-stage throttling intermediate incomplete cooling dual-compression cycle heat pump system + front mechanical subcooling（OTHS+FMC） could effectively reduce the optimal high pressure of the two-stage cycle system. When the evaporation temperature was -30 ℃， its COP could be increased by up to 12.70% compared with the initial transcritical CO₂ heat pump system， with a 5.08% COP improvement under optimal high pressure. The economic analysis showed that the initial investment cost of OTHS+FMC was higher， but the energy efficiency improvement and emission reduction benefits of long-term operation made it more environmentally economical.

Key words: transcritical CO₂ heat pump, heating system, heating performance, economic analysis, cycle optimization

CLC Number:

TK172

HUANG Shuai, XIANG Xinyu, LI Ang, JIN Xu, Aruna , ZHANG Jiapeng. Cycle optimization and environmental economic evaluation of transcritical CO₂ heat pump heating systems[J]. Integrated Intelligent Energy, 2026, 48(4): 81-89.

Figures/Tables 15

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Table 1

Theoretical calculation formulas of power consumption and heating capacity of each heat pump system

热泵	W_total	Q_H
单级循环	${q}_{m}({h}_{\mathrm{c}\mathrm{o}\mathrm{m},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{c}\mathrm{o}\mathrm{m},\mathrm{i}\mathrm{n}})$	${q}_{m,\mathrm{g}\mathrm{a}\mathrm{s}}({h}_{\mathrm{g}\mathrm{a}\mathrm{s},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{g}\mathrm{a}\mathrm{s},\mathrm{i}\mathrm{n}})$
双级循环	$\begin{array}{l}{q}_{m,\mathrm{H}}({h}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{H},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{H},\mathrm{i}\mathrm{n}})+\\ {q}_{m,\mathrm{L}}({h}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{L},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{L},\mathrm{i}\mathrm{n}})\end{array}$	${q}_{m,\mathrm{g}\mathrm{a}\mathrm{s}}({h}_{\mathrm{g}\mathrm{a}\mathrm{s},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{g}\mathrm{a}\mathrm{s},\mathrm{i}\mathrm{n}})$
机械过冷+ 双级循环	$\begin{array}{l}{q}_{m,\mathrm{H}}({h}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{H},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{H},\mathrm{i}\mathrm{n}})+\\ {q}_{m,\mathrm{L}}({h}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{L},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{L},\mathrm{i}\mathrm{n}})+\\ {q}_{m,\mathrm{M}\mathrm{c}}({h}_{\mathrm{M}\mathrm{c},\mathrm{c}\mathrm{o}\mathrm{m},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{M}\mathrm{c},\mathrm{c}\mathrm{o}\mathrm{m},\mathrm{i}\mathrm{n}})\end{array}$	$\begin{array}{l}{q}_{m,\mathrm{g}\mathrm{a}\mathrm{s}}({h}_{\mathrm{g}\mathrm{a}\mathrm{s},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{g}\mathrm{a}\mathrm{s},\mathrm{i}\mathrm{n}})+\\ {q}_{m,\mathrm{M}\mathrm{c}}({h}_{\mathrm{M}\mathrm{c},\mathrm{c}\mathrm{o}\mathrm{m},\mathrm{o}\mathrm{u}\mathrm{t}}-{h}_{\mathrm{M}\mathrm{c},\mathrm{c}\mathrm{o}\mathrm{m},\mathrm{i}\mathrm{n}})\end{array}$

Table 1

Table 2

Table 3

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设备	公式	编号
低压级压缩机	${C}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{L}}=10\mathrm{ }167.5\mathrm{ }{W}^{0.46}$	(3)
高压级压缩机	${C}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{H}}=9\mathrm{ }624.2\mathrm{ }{W}^{0.46}$	(4)
R134a压缩机	${C}_{\mathrm{c}\mathrm{o}\mathrm{m},\mathrm{R}134\mathrm{a}}=758.15\mathrm{ }{W}^{0.872\mathrm{ }8}$	(5)
套管式换热器	C_{HX,tube-in-tube} = 2 382.4 A^0.68	(6)
板式换热器	${C}_{\mathrm{H}\mathrm{X},\mathrm{P}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{e}}=1\mathrm{ }874.4\mathrm{ }{A}^{0.983\mathrm{ }5}$	(7)

污染物	a_g/[kg∙(kW∙h)^-1]	b_g/(元∙t^-1)
CO₂	0.997	34.94
SO₂	0.030	2.50
NO_x	0.015	5.00