Numerical study on thermal performance of multirow helically coiled tube heat exchanger for surface water heat pump system

2021 ◽  
Vol 44 ◽  
pp. 100982
Author(s):  
Chaohui Zhou ◽  
Long Ni ◽  
Yang Yao
Keyword(s):  
Heat Exchanger ◽  
Surface Water ◽  
Heat Pump ◽  
Thermal Performance ◽  
Numerical Study ◽  
Pump System ◽  
Heat Pump System ◽  
Coiled Tube ◽  
Tube Heat Exchanger ◽  
Helically Coiled Tube

scholarly journals Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1762 ◽  
Author(s):  
Zhe Wang ◽  
Fenghui Han ◽  
Yulong Ji ◽  
Wenhua Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Transfer Model ◽  
Enhanced Heat Transfer ◽  
Pump System ◽  
Heat Pump System ◽  
Tube Heat Exchanger ◽  
Exergy Transfer

A marine seawater source heat pump is based on the relatively stable temperature of seawater, and uses it as the system’s cold and heat source to provide the ship with the necessary cold and heat energy. This technology is one of the important solutions to reduce ship energy consumption. Therefore, in this paper, the heat exchanger in the CO2 heat pump system with graphene nano-fluid refrigerant is experimentally studied, and the influence of related factors on its heat transfer enhancement performance is analyzed. First, the paper describes the transformation of the heat pump system experimental bench, the preparation of six different mass concentrations (0~1 wt.%) of graphene nanofluid and its thermophysical properties. Secondly, this paper defines graphene nanofluids as beneficiary fluids, the heat exchanger gains cold fluid heat exergy increase, and the consumption of hot fluid heat is heat exergy decrease. Based on the heat transfer efficiency and exergy efficiency of the heat exchanger, an exergy transfer model was established for a seawater source of tube heat exchanger. Finally, the article carried out a test of enhanced heat transfer of heat exchangers with different concentrations of graphene nanofluid refrigerants under simulated seawater constant temperature conditions and analyzed the test results using energy and an exergy transfer model. The results show that the enhanced heat transfer effect brought by the low concentration (0~0.1 wt.%) of graphene nanofluid is greater than the effect of its viscosity on the performance and has a good exergy transfer effectiveness. When the concentration of graphene nanofluid is too high, the resistance caused by the increase in viscosity will exceed the enhanced heat transfer gain brought by the nanofluid, which results in a significant decrease in the exergy transfer effectiveness.

scholarly journals COMPARISON OF FROST AND DEFROST PERFORMANCE BETWEEN MICROCHANNEL COIL AND FIN-AND-TUBE COIL FOR HEAT PUMP SYSTEMS

2011 ◽  
Vol 19 (04) ◽  
pp. 273-284 ◽  
Author(s):  
SANKAR PADHMANABHAN ◽  
LORENZO CREMASCHI ◽  
DANIEL FISHER
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Cycle Time ◽  
Cycling Performance ◽  
Residual Water ◽  
Pump System ◽  
Heat Pump System ◽  
Tube Heat Exchanger ◽  
Microchannel Heat Exchanger ◽  
Dry Conditions

This paper presents a comparison of frost and defrost cycling performance between a microchannel heat exchanger with louvered fin and a fin-and-tube heat exchanger with straight fins employed as outdoor coils of a 14 kW (48 000 Btu/h) heat pump system. In addition to temperature, pressure and flow rate measurements taken at various locations of the systems, the fin-base and tube wall surface temperature were also recorded by using fine-gauge precalibrated thermocouples on the coils. Further, load cells were used to measure the mass of frost accumulation during heating tests. Data showed that the frosting time of the microchannel heat exchanger is more than 50% shorter than for the fin-and-tube heat exchanger, which is chosen as the baseline system. The average heating capacity and system performance over a frost–defrost cycle are also lower for the system with microchannel heat exchangers. Higher frost growth rate was mainly due to augmented temperature difference between air and the surface of the heat exchanger, and preferential frost nucleation sites on the louvered fins and microchannel tubes. Removal of residual water in the microchannel heat exchanger did not improve the frost performance significantly. Blowing nitrogen on the microchannel coil after defrost removed any visible water retained in the coil after the defrost cycle but the cycle time increased only by 4% with respect to wet and frost conditions. The cycle time of the same microchannel coil starting with dry conditions was about 60% longer than the cycle time in wet and frost conditions.

Key Problem Analysis and Solution on Intake Water and Heat Transfer of Sewage-Source Heat Pump System

2014 ◽  
Vol 1070-1072 ◽  
pp. 1799-1802
Author(s):  
Hai Yang Bi ◽  
Yong Mao Shang ◽  
Xiang Hong Gu
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Waste Heat ◽  
Problem Analysis ◽  
Pump System ◽  
Heat Pump System ◽  
Technology Application ◽  
Tube Heat Exchanger ◽  
Sewage Source

Changing "high consumption energy, low temperature heat to the indoor, waste heat to the environment", and turning the HVAC harmoniously into the natural ecological cycle, conform to the trend of the development of ecological architecture. Heat pump technology is a way of HVAC energy saving the most practical. Although low heat and cold source of the city sewage is ideal, but the quality is very unstable, can not meet the operation requirements of heat exchange equipment. This paper analyzes the key problems of the sewage side in sewage source heat pump technology application in the present: hair dirt clog sewage heat exchanger; fouling in heat surface reduces the heat transfer performance, and results in large heat-transfer equipment in the practical application. According to the key problems of sewage side, this paper prevents hair clogged with large tube heat exchanger; reduces the fouling thermal resistance, and enhances heat transfer process using the heat exchanging technology of circulating fluidized bed.

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