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. 2022 Nov 25:217:119256.
doi: 10.1016/j.applthermaleng.2022.119256. Epub 2022 Sep 3.

Integrated system of exhaust air heat pump and advanced air distribution for energy-efficient provision of outdoor air

Sheng Zhang  1 , Weigeng Yun  2 , Zhang Lin  3
Affiliations

Integrated system of exhaust air heat pump and advanced air distribution for energy-efficient provision of outdoor air

Sheng Zhang et al. Appl Therm Eng. .

Abstract

A large outdoor air supply is required to control the airborne infection risk of respiratory diseases (e.g., COVID 19) but causes a high energy penalty. This study proposes a novel integrated system of the exhaust air heat pump and advanced air distribution to energy-efficiently provide outdoor air. The system energy performances are evaluated by the experimentally validated thermodynamic model of heat pump and heat removal efficiency model of advanced air distribution. Results show the exhaust air heat pump with advanced air distribution can save energy because of three mechanisms. First, the exhaust air heat pump reuses the exhaust air to reduce the condensation temperature, thereby improving the coefficient of performance. Second, advanced air distribution reduces ventilation load. Third, advanced air distribution reduces the condensation temperature and enhances the evaporation temperature, thereby improving the coefficient of performance. The exhaust air heat pump saves energy by 18%, advanced air distribution saves energy by 36%, and the integrated system of the exhaust air heat pump and advanced air distribution can save energy by 45%. As a specific application, compared with the conventional system (i.e., the outdoor air heat pump with mixing ventilation), the exhaust air heat pump with stratum ventilation saves energy by 21% - 35% under various outdoor air ratios and outdoor air temperatures. The proposed integrated system of the exhaust air heat pump and advanced air distribution contributes to the development of low-carbon and healthy buildings.

Keywords: Advanced air distribution; Exhaust air heat pump; Heat removal efficiency; Outdoor air supply.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Schematic of outdoor air heat pump.
Fig. 2
Fig. 2
Schematic of exhaust air heat pump.
Fig. 3
Fig. 3
Schematic of pressure-enthalpy diagram.
Fig. 4
Fig. 4
Schematics of different air distributions.
Fig. 5
Fig. 5
Comparisons of predicted COP with measured COP.
Fig. 6
Fig. 6
Errors of predicted COP of different experiment cases.
Fig. 7
Fig. 7
Variations of supply air temperature and exhaust air temperature with heat removal efficiency.
Fig. 8
Fig. 8
Variations of total cooling load and ventilation load with heat removal efficiency.
Fig. 9
Fig. 9
Variations of condensation temperatures of outdoor air heat pump (OAHP) and exhaust air heat pump (EAHP) with heat removal efficiency.
Fig. 10
Fig. 10
Variations of COPs of outdoor air heat pump (OAHP) and exhaust air heat pump (EAHP) with heat removal efficiency.
Fig. 11
Fig. 11
Variations of evaporation temperatures of outdoor air heat pump (OAHP) and exhaust air heat pump (EAHP) with heat removal efficiency.
Fig. 12
Fig. 12
Variations of power consumptions of outdoor air heat pump (OAHP) and exhaust air heat pump (EAHP) with heat removal efficiency.
Fig. 13
Fig. 13
Schematic of stratum-ventilated classroom .
Fig. 14
Fig. 14
Comparisons of measured and predicted heat removal efficiencies (HRE) of stratum ventilation.
Fig. 15
Fig. 15
Variations of total cooling loads of outdoor air heat pump with mixing ventilation (OAHP-MV) and exhaust air heat pump with stratum ventilation (EAHP-SV) with outdoor air ratio.
Fig. 16
Fig. 16
Variations of COPs of outdoor air heat pump with mixing ventilation (OAHP-MV) and exhaust air heat pump with stratum ventilation (EAHP-SV) with outdoor air ratio.
Fig. 17
Fig. 17
Energy saving by exhaust air heat pump with stratum ventilation compared with outdoor air heat pump with mixing ventilation considering effect of outdoor air ratio.
Fig. 18
Fig. 18
Variations of total cooling loads of outdoor air heat pump with mixing ventilation (OAHP-MV) and exhaust air heat pump with stratum ventilation (EAHP-SV) with outdoor air temperature.
Fig. 19
Fig. 19
Variations of COPs of outdoor air heat pump with mixing ventilation (OAHP-MV) and exhaust air heat pump with stratum ventilation (EAHP-SV) with outdoor air temperature.
Fig. 20
Fig. 20
Energy saving by exhaust air heat pump with stratum ventilation compared with outdoor air heat pump with mixing ventilation considering effect of outdoor air temperature .
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