THERMAL SCIENCE

International Scientific Journal

Thermal Science - Online First

Yuanyuan Liu

,

Tianxiang Jia

,

Jing Wang

,

Yang Li

,

Jun Zhao

,

Yaze Wang

,

Xinlei Liang

online first only

Research on the energy efficiency improvement of closed loop wastewater source heat pump with direct-expansion heat exchanger

ABSTRACT
The closed-loop wastewater source heat exchanger (WSHE) has advantages such as being non-clogging and resistant to corrosion, but their heat transfer efficiency is relatively low, therefore it is still not the mainstream form of heat exchanger of wastewater source heat pump (WSHP). A novel CO2 direct-expansion wastewater source heat exchanger (DX-WSHE) is proposed in this paper, aiming to significantly improve the heat transfer rate of the heat exchanger and the energy efficiency of the heat pump system. The direct-expansion heat transfer process is complex, large grid number and long calculation time will be required if calculated by conventional numerical simulation software. Therefore, a three-dimensional transient heat transfer model was developed based on the thermal resistance and capacity model, which offers the advantages of fast computation speed and strong flexibility. The heat transfer and energy efficiency characteristics under different parameters were studied. The coefficient of performance (COP) of the direct-expansion wastewater source heat pump (DX-WSHP) can be increased by 31.0% compared to conventional design, and the heat flux of the direct-expansion wastewater source heat exchanger can be up to 250 W/m for the standard group. Compared with conventional designs, the direct-expansion wastewater source heat pump has excellent heat transfer and energy efficiency capabilities, which is a promising building energy saving and emission reduction technology.
KEYWORDS
wastewater source heat pump, direct-expansion heat exchanger, thermal resistance and capacity model, numerical simulation
PAPER SUBMITTED: 2023-12-23
PAPER REVISED: 2024-02-19
PAPER ACCEPTED: 2024-03-14
PUBLISHED ONLINE: 2024-05-18
DOI REFERENCE: https://doi.org/10.2298/TSCI231223115L
REFERENCES
  1. Mladen Bošnjaković, et al., BUILDING INTEGRATED PHOTOVOLTAICS. OVERVIEW OF BARRIERS AND OPPORTUNITIES, Thermal Science, 27(2023), 2B, pp. 1433-1451
  2. Fang Xiaomin, Li Xiaolu, SOLAR PHOTOVOLTAIC POWER STATION SYSTEM BASED ON COMPOSITE HEAT SOURCE THERMAL POWER TECHNOLOGY, Thermal Science, 27(2023), 2A, pp. 967-973
  3. Xu Tongyu, et al., Integration of sewage source heat pump and micro-cogeneration system based on domestic hot water demand characteristics: A feasibility study and economic analysis, Process Safety and Environmental Protection, 179(2023), pp. 796-811
  4. Shen Chao, et al., A review on the current research and application of wastewater source heat pumps in China, Thermal Science and Engineering Progress, 6(2018), pp. 140-156
  5. Du Yuji, et al., The potential of wastewater-source heat pump in decarbonizing buildings sector of China, Environmental technology, 2023, pp. 31-30
  6. Ozcan Huseyin Gunhan, et al., Energy, exergy, economic, environmental and sustainability (4ES) analyses of a wastewater source heat pump system for district heating applications based on real operational data, Sustainable Energy Technologies and Assessments, 56(2023), pp. 103077
  7. Wang Qiang, et al., Experiments on the characteristics of a sewage water source heat pump system for heat recovery from bath waste, Applied Thermal Engineering, 204(2022), pp. 117956
  8. Zhang Qunli, et al., Experimental evaluation of heat transfer performance of falling film evaporator for wastewater source heat pump with backwash system, International Journal of Refrigeration, 113(2020), pp. 80-93
  9. Liu Y, et al., VERTICAL U-SHAPED HEAT EXCHANGERS FOR CONSTRUCTION ENGINEERING: NEW PROMISES AND FUTURE CHALLENGES, Thermal Science, 25(2021), 3B, pp. 2253-2261
  10. Jokić I A, et al., FEASIBILITY OF CLOSED LOOP GROUND SOURCE HEAT PUMP FOR RESIDENTIAL HEATING AND COOLING APPLICATIONS IN SERBIA, Thermal Science, 24(2020), 2A, pp. 96-976
  11. Gao Yuefen, Gao Tingting, Simulation study on the performance of direct expansion geothermal refrigeration system using carbon dioxide transcritical cycle, in: Energy Procedia, Elsevier Ltd, Hong Kong, 2019, pp. 5479-5487
  12. A. Nguyen, et al., Pressure-enthalpy coupled thermal resistance and capacity model (PH-TRCM) for direct-expansion borehole heat exchangers: Application for supercritical CO2, Geothermics, 76(2018), pp. 50-59
  13. Ghazizade-Ahsaee H, Ameri M, Energy and Exergy Investigation of a Carbon Dioxide Direct-Expansion Geothermal Heat Pump, Applied Thermal Engineering, 129(2018), pp. 165-178
  14. Ghazizade-Ahsaee H, Ameri M, Effects of using expander and internal heat exchanger on carbon dioxide direct-expansion geothermal heat pump, Applied Thermal Engineering, 136(2018), pp. 389-407
  15. Ghazizade-Ahsaee H, et al., A comparative exergo-economic analysis of four configurations of carbon dioxide direct-expansion geothermal heat pump, Applied Thermal Engineering, 163(2019), C, pp. 114347
  16. Lemmon E W, et al., NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP, in: National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, 2013
  17. Eslami-Nejad P, et al., A quasi-transient model of a transcritical carbon dioxide direct-expansion ground source heat pump for space and water heating, Applied Thermal Engineering, 91(2015), pp. 259-269
  18. Li Y, et al., Dynamic heat transfer analysis of a direct-expansion CO2 downhole heat exchanger, Applied Thermal Engineering, 189(2021), pp. 116733
  19. Austin B T, Sumathy K, Parametric study on the performance of a direct-expansion geothermal heat pump using carbon dioxide, Applied Thermal Engineering, 31(2011), 17, pp. 3774-3782
PDF VERSION [DOWNLOAD]
Research on the energy efficiency improvement of closed loop wastewater source heat pump with direct-expansion heat exchanger