Abstract
The performance of a CO2 double-pipe evaporator was studied through experiments and a simulation model that was established by the steady-state distribution parameter method and experimentally verified while using a CO2 transcritical water‒water heat pump system. The effects of different operating parameters on heat transfer performance were studied over a range of evaporation temperatures (−5 to 5 °C), mass velocity (100‒600 kg/m2s), and heat flux (5000‒15,000 W/m2). It was found that the dryout quality increased at a small evaporation temperature, a large mass velocity, and a small heat flux. The simulation yield means relative error (RE) of heat transfer for the evaporation temperature and that of the CO2 pressure drop for the chilled water inlet temperature were 5.21% and 3.78%, respectively. The effect of tube diameter on the performance of CO2 double-pipe evaporator is probed through simulations. At the same time, this paper defines a parameter α , which is the proportion of the pre-dryout region to the whole heat transfer region. A larger α value is desirable. A further theoretical basis is provided for designing an efficient and compact CO2 evaporator.
Highlights
Significant attention has been directed towards alternative energy conversion systems due to environmental concerns [1]
This paper studies the performance of CO2 double-pipe evaporators for transcritical CO2 through experiments and a simulation model that was established by steady-state distribution parameter method
The dryout, which causes a drop in the heat transfer coefficient, forms two regions: the pre-dryout and post-dryout
Summary
Significant attention has been directed towards alternative energy conversion systems due to environmental concerns [1]. Rin et al [10] used the finite volume method to predict the performance of an evaporator for a CO2 air-conditioning system. Kravanja et al [13] developed a double pipe heat exchanger and investigated. Patino et al [15] developed a finite-volume mathematical model to study a concentric counter-current evaporator for CO2. The special properties of CO2 pose serious challenges to the design and optimization of conventional heat exchangers [23]. CO2 refrigeration systems due to the high operating pressure of these systems, as well as the special thermophysical and transport properties of CO2 in the near-critical region to design efficient and compact heat exchangers. This paper studies the performance of CO2 double-pipe evaporators for transcritical CO2 through experiments and a simulation model that was established by steady-state distribution parameter method. This paper defines one parameter, α, the proportion of pre-dryout region to the whole heat transfer region
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
