| Tibetan area of western Sichuan has the characteristics of abundant hydropower resources,high cost of traditional fossil fuel transportation,fragile ecological environment and small building density,etc.The electric-driven air source heat pump(ASHP)has broad application prospects,but it is faced with low temperatures and frost problems in the application process in Tibetan area of western Sichuan.With the improvement of technology and principle,the unit can operate stably under the environmental conditions in Tibetan area of western Sichuan,but the problem of frost formation still needs to be improved.The frost formation in Tibetan area of western Sichuan has its special characteristic.Firstly,the differences in temperature and humidity conditions between counties and cities lead to uneven distribution of frost and spatiotemporal distribution.Secondly,there is a low temperature and high relative humidity environment in some regions,resulting in heavy frost formation at low temperature.Therefore,it is necessary to study the spatial and temporal distribution characteristics of frost formation in Tibetan area of western Sichuan,and to develop effective anti-frost technology,thereby alleviating the problem of declining heating caused by frost formation.The sub-region frosting map is an effective tool for studying the characteristics of spatio-temporal distribution of frost,with the form of a two-dimensional map of temperature and relative humidity.However,Tibetan area of western Sichuan has large altitude spans,and it is necessary to study the influence of atmospheric pressure on the map.A general and relatively accurate cold plate frosting model is used to study thevariation of frosting rate with atmospheric pressure and using atmospheric pressure as a variable.The results show that there is a curve where the frosting rate does not change with the atmospheric pressure in the frosting area of the sub-region frosting map.The frosting rate decreases above this curve with the altitude is rises.The frosting rate increases below this line with the altitude is rises.In general,the degree of change is not great.In order to meet the research needs,the frosting map is extended in the low-temperature region.The temperature and humidity data are expressed in the low temperature extension spectrum,linearity difference method is used to obtain the frosting rate data,and then the frosting frequency data is obtained,and then the spatio-temporal distribution of the frosting frequency is explored.The results show that the spatial distribution of frosting frequency in heating season is gradually weakened from east to northeast to southwest;there are three types of monthly frosting frequency: "U","up" and "down".Frosting is severe at night and slight during the day.According to the characteristics of the spatial and temporal distribution of frost,an effective frost suppression strategy is proposed in the design and operation of the unit.The principle of the frost-resisting ratio is ‘more frosting frequency,more repression’.Based on the spatial distribution characteristics of the frosting frequency,the average frosting frequency in the heating seasons of each county and city is reduced to the corresponding frost suppression target,the corresponding evaporating temperature adjustment value of the unit design is given.Based on the characteristics of time distribution of frost frequency,the average frosting frequency of each month or some periods in the heating season of each county/city is reduced to the corresponding frost suppression target,there will be given the corresponding evaporating temperature rise value of the unit operation.Based on the correlation between the evaporating temperature increase value and temperature-humidity,the estimate formula for the unit design and operation evaporating temperature adjustment value is given.Based on the effective suppression method of frost,the sub-resign frosting map is revised,and the corresponding 0.2,0.5,0.9,1.3 mm/h frost rate line fitting formula and map is given. |
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