Study On Operation Characteristics Of Offshore Shallow-buried Capillary Seawater Source Heat Pump System

The ocean is a vast reservoir of renewable energy,and when solar radiation enters the ocean,some of it turns into kinetic energy for ocean currents,much more is being converted into low-grade energy that can't be used directly and stored in seawater.The heat capacity of seawater is much larger than that of air,so seawater is very suitable for use as a natural cold/heat source in the HVAC field.seawater corrosion,marine biological adhesion and high cost of water intake are common problems in the open system widely used in Marine source heat pump,however,the closed spiral coil system has the problem of short circuit of heat flow,which will greatly affect the heat transfer efficiency.At present,the capillary network made into a cage as the front heat exchanger of the sea source heat pump buried in the seabed,can avoid the above problems,and has a good heat transfer performance.This paper studies the performance of the offshore shallow buried capillary sea source heat pump system.firstly,the heat transfer mathematical models of shallow buried capillary heat exchanger,underground soil and offshore seawater were established;secondly,long-term experimental tests were conducted on the system in winter and summer with the sea water source heat pump experimental platform,process test data and analyze the operating characteristics of the system under experimental conditions;then,based on the heat transfer model and relying on the TRNSYS platform,the capillary heat exchanger module and capillary heat pump system model were established,experimental data were used to verify the accuracy of the model;finally,the system model is used for simulation study,the influence of the pipe velocity,seepage velocity,sea water temperature and the number of heat exchanger opening groups on the performance of the heat pump system was analyzed in winter and summer.Experimental findings: under the most unfavorable conditions in winter and summer,the system could meet the hotel load demand.After the heat pump was continuously operated for 24 hours,the mean COP of unit and system in winter was 3.96 and 3.08,and the mean EER of unit and system in summer was 4.24 and 3.34,respectively.simulation findings: under adverse conditions in winter and summer,with the increase of the flow rate in the tube,the performance coefficient of the heat pump unit shows an upward trend,the performance coefficient of the heat pump system shows a downward trend,and the heat transfer per unit area shows an upward trend,but the variation range of each amount is less than 10%.winter and summer adverse conditions,with the increase of seepage velocity,the performance coefficient of unit and system and the unit area heat transfer of capillary tube all show a great increase trend.under adverse conditions in winter,the unit system performance coefficient and unit area heat transfer of capillary increased with seawater temperature;under unfavorable conditions in summer,the unit system performance coefficient and unit area heat transfer of capillary decreased with the increase of seawater temperature.in the early or late heating/cooling season,in this paper,when the number of heat exchanger opening groups of the heat pump system is 4,the performance coefficient of the system and the unit is the best,and the system is in the best energy saving state.Compared with the total number of heat exchangers,running a heating season can save 2275 KWH of electricity.In practical engineering,load satisfaction rate can be introduced to judge whether the system can meet the load and analyze the system's relative energy saving.The shallow-buried capillary heat pump system has a better energy supply effect under adverse working conditions;compared with tube velocity and sea water temperature,the seepage strength of seabed has a great influence on the heat transfer of capillary heat exchanger;when the load is small,adjust the number of heat exchanger opening groups so that the load satisfaction rate is slightly greater than 1,it can save energy sufficiently and has certain significance for practical engineering application.