Study On Convective And Radiative Heat Dissipation Ratio Of Indoor Electric Equipment In Radiant Cooled Rooms

The distribution ratio of convection and radiation of indoor various kinds of internal disturbance heat is the key input parameter of room thermal process simulation calculation and load calculation.The accuracy of distribution ratio directly affects the accuracy of airconditioning load calculation.The convection and radiation distribution ratio of various kinds of indoor intrusive heat in radiation-cooled air conditioning environment is different from that in convection-cooled air conditioning environment.At present,there is a lack of convection and radiation distribution ratio of various types of internal heat gain under radiation air conditioning.In view of the above research background,this paper studies the convection and radiation heat dissipation ratio of indoor equipment under radiation cooling environment,and mainly carries out the following research work:Firstly,according to the experimental requirements,a concrete radiation cooling experimental room with an external size of 2480mm×2480mm×2660mm was built in a relatively stable temperature environment,and an external water system was built by using a constant temperature water bath as a cold and heat source.According to the principle of radiation heat transfer,the method of net radiometer is used to separate the convective heat loss and radiation heat loss of the equipment,and a set of automatic scanning test system of 5-axis net radiation quantity is designed and made,which can realize the automatic measurement of radiation flux on five surfaces.The measurement system can automatically measure the radiative heat of the heat source,which creates the conditions for the experiment.Secondly,in the typical working condition of radiant roof cooling,the relationship between the nameplate power and actual power consumption of the equipment is studied,and the reasons for the difference between the two are analyzed.Then,the radiative heat loss of common indoor equipment is measured experimentally by using the five-axis automatic testing system of net radiation amount.The ratio of convection and radiation heat dissipation of indoor cooling equipment under the typical working condition is obtained.The test results show that the actual power consumption of most equipment is far lower than the nameplate value.The actual power consumption of computer and printer is only about 10% of the nameplate power,the power consumption of monitor is 12%～66% of the nameplate power,and the actual power consumption of notebook computer is only 12%～30% of the nameplate value.The radiative heat dissipation ratio of the computer is about 20%,the radiative heat dissipation ratio of the monitor is 38%～55%,the radiative heat dissipation ratio of the notebook computer is 30%～40%,the radiative heat dissipation ratio of the printer is 28%～36%,the radiative heat dissipation ratio of the projector is 16%～20%.Finally,considering that the radiative cooling air conditioning has a variety of end laying forms,and the radiation heat dissipation of the equipment is related to the surface emissivity of the equipment,the surface temperature of the equipment,the surface temperature of the enclosure structure,the surface emissivity of the enclosure structure and other factors.Therefore,the influence of different cold wall positions and different water supply temperatures on the radiation heat dissipation ratio of the equipment is studied,which provides a reference for the radiation heat dissipation ratio of the equipment under various radiation cooling conditions.The test results show that the radiative ratio of different equipment has different sensitivities to different positions of the cold wall.The radiative cooling ratio of the display is about 6.4% higher than that of the floor and 3% higher than that of the roof under the condition of wall radiative cooling.The radiative heat dissipation ratio of computers,laptops,printers and projectors in the floor radiative cooling condition is 2.99%,1.78%,5.4% and 1.91%,respectively,compared with that in the wall radiative cooling condition.The average values of radiant cooling condition higher than roof are 3.94%,2.74%,7.16% and 2.85%.With the increase of water supply temperature on the cold wall,the radiation heat dissipation of the equipment decreases.In the working condition of wall radiant cooling,when the water supply temperature on the cold wall rises from 18℃ to 22℃,the radiative heat dissipation ratio of computers,monitors,laptops,printers and projectors decreases by 3.02%,8.95%,3.57%,4.22%and 1.34%,respectively.Under the condition of radiant floor cooling,when the water supply temperature on the cold wall rises from 18℃ to 22℃,the radiative heat dissipation ratio of computers,monitors,laptops,printers and projectors decreases by 3.46%,6.27%,4.48%,3.91%and 1.9%,respectively.Under the roof radiation cooling condition,when the water supply temperature on the cold wall rises from 18℃ to 22℃,the radiation heat dissipation ratio of computers,monitors,laptops,printers and projectors decreases by 2.21%,3.24%,4.06%,3.83%and 1.15%,respectively.The research results of this paper obtain the convection and radiation heat dissipation ratio of common indoor cooling equipment under radiation cooling,which provides basic parameters for the load calculation of the room under radiation air-conditioning.