Performance of Coupled High-Temperature Heat Pump with Steam Supply Through Long-Distance Hot-Water Pipeline

Combined heat and power centralized heating can supply steam to surrounding industrial enterprises by using the steam from turbine, which is an efficient way of steam supply. However, as the supply distance increases, the temperature drop and pressure loss of the steam become severe. This study aims to propose a new absorption-compression coupled high-temperature heat pump cycle system, which uses the existing combined heat and power pipeline network to transport hot water and generates steam at the user site, effectively expanding the coverage of combined heat and power steam supply. In this paper, a thermodynamic simulation model of the heat pump system is established, and the influences of the supply water temperature of the primary network, the temperature of the micro-pressure steam, and the steam supply temperature on the performance of the heat pump are analyzed in detail.

This study combines the absorption heat exchanger with the vapor compression heat pump, and proposes an absorption-compression coupled high-temperature heat pump cycle system. This paper uses theoretical simulation methods to analyze the influence of key parameters on the performance of the heat pump system. Based on the principles of energy conservation and mass conservation, the thermodynamic steady-state model of the system is established, and the thermodynamic equations are solved using the engineering equation solver (EES) software. Through parameter sensitivity analysis, the effects of the supply water temperature of the primary network, the micro-pressure steam temperature, and the steam supply temperature on the system performance are studied.

The higher the supply temperature of the primary network, the greater the capacity of the absorption heat exchanger to increase the temperature, the larger the COP of the coupled system, and the lower the unit steam consumption. When the supply water temperature is 120 ℃ and the steam generated is 180 ℃, the temperature rise coefficient of the absorption heat exchanger is 0.37. The coupled system COP is 2.56, and the unit steam consumption is 292.5 kW∙h/(t/h). Compared with the case where the supply water temperature is 95 ℃, the COP increases by 2.7%, and the unit steam consumption decreases by 2.5%. As the temperature of the micro-pressure steam increases from 75 ℃ to 100 ℃, the COP of the coupled system first increases and then decreases, and the unit steam consumption first decreases and then increases. When the temperature of the micro-pressure steam is 80 ℃, the COP of the coupled system is the maximum value of 2.6, and the unit steam consumption is the minimum value of 285.3 kW∙h/(t/h). As the steam supply temperature increases, the COP of the coupled system monotonically decreases, and the unit steam consumption monotonically increases. When the steam supply temperature increases from 100 ℃ to 200 ℃, the COP of the coupled system decreases from 4.3 to 2.3, and the unit steam consumption increases from 166.2 kW∙h/(t/h) to 316.0 kW∙h/(t/h).

The absorption-compression coupled high-temperature heat pump system proposed in this paper provides an effective solution for long-distance hot water supply to steam. The supply water temperature of the primary network, the micro-pressure steam temperature, and the steam supply temperature are the key factors affecting the system performance. This system offers a feasible approach for expanding the steam supply range of combined heat and power and improving the comprehensive energy utilization rate.