Analysis of a New Super High Temperature Hybrid Absorption-Compression Heat Pump Cycle

Abstract

Utilization of high-temperature energy in industrial production processes is often exhausted by huge low-temperature waste heat without recovery. Thus, energy efficiency is quite limited. Heat pumps are widely used as a high-efficiency waste heat recovery system and are divided into vapor compression cycle, driven by electricity, and absorption type, driven by steam or hot water. However, compression heat pumps are quite difficult to reach more than 100 °C due to the temperature and compression limits of compressors and the working medium. Meanwhile, the COP (coefficient of performance) of an absorption heat pump is quite low due to the thermodynamic cycle characteristics. In order to increase the outlet temperature and COP significantly, a new type of compression-absorption hybrid heat pump cycle is presented and simulated. Compared with traditional cycles, this heat pump can reach the heat sink temperature of 200 °C with a highly satisfactory COP. This heat pump could reach the optimal COP of 3.249 when the pressure ratio of the compressor is 6.5, the coupling temperature of the low-pressure stage is 55 °C and the coupling temperature of the high-pressure stage is 73 °C. Exergy analysis shows that evaporators and condensers show better efficiency. This heat pump could be promising in different kinds of heat recovery.

Optimizing the Recovery of Latent Heat of Condensation from the Flue Gas Stream through the Combustion of Solid Biomass with a High Moisture Content

“…Absorption and compressor heat pumps deserve special attention. These are solutions that are being used with increasing frequency [20][21][22]. They significantly increase the efficiency of the system.…”

A Review of Super-High-Temperature Heat Pumps over 100 °C

“…Schweigler [59] directly integrated the high-speed turbo-compressor into the single-stage water/lithium bromide absorption heat pump cycle, and studied the cycle characteristics of three different operating modes through detailed steady-state thermal process simulation. A compression ratio of 3 allows a rise in the cooling water inlet temperature by 10 K, and enables the use of low-temperature waste heat below 70 • C. Sun [60] put the compressor between the generator and the absorber, producing a heating temperature of the new system up to 125 • C. In order to obtain a heating temperature above 100 °C, Sun [61] coupled the compression cycle with the second absorption cycle type, as shown in Figure 5c; the hot water temperature could reach 135 °C and the COP was 3.6. Gao [62,63] proposed a new type of air source hybrid heat pump, as shown in Figure 5d.…”

“…Zhang [64] proposed a new system coupling a two-stage cascade heat pump with an absorption heat pump, and found that the new system would be more advantageous when the heating temperature lift was more than 150 °C. In order to obtain a heating temperature above 100 • C, Sun [61] coupled the compression cycle with the second absorption cycle type, as shown in Figure 5c; the hot water temperature could reach 135 • C and the COP was 3.6. Gao [62,63] proposed a new type of air source hybrid heat pump, as shown in Figure 5d.…”

Investigation of the Concentric Heat Pump with Improved Energy Performance

“…A SWOT analysis is offered for easy selection of types of energy sources for constructing a polyvalent system [8]. Researchers from China have proposed a new type of hybrid compressionabsorption heat pump, in which compared with traditional radiator cycles, the temperature is increased to 200°C and COP to 3.249, with very satisfactory performance of the evaporator and condenser [15]. The investigated system consists of 3 air-to-water HVAC units, 1 water storage tank, and 1 fan coil unit (FCUs) for cooling and heating; a threesection greenhouse under local climate conditions confirmed stable heating but insufficient cooling [16].…”