Study On Thermal Performance Of The Heating Radiator In Cold Regions With High Altitude

Presently in China, there is a lack of explicit technical regulations for theapplication of heating equipment in high altitude cold regions. There are hardly anymanufacturers engaged in the production of special equipment for these regions. Andthere are only a few researches regarding the influences of extreme weather conditionson equipment performance. When it comes to the selection of parameter correctioncoefficient for high altitude regions, many designers rely on experience and have nospecific correction methods, which is unscientific and may lead to indoor discomfort aswell as a waste of energy. So, developing a correction method for the selection ofequipment in high altitude cold regions has great practical significance.Based on classical heat transfer model, this thesis analyzed the thermalperformance of3types of radiators in high-altitude areas through theoretical analysis,numerical simulation and experimental research, and draw a correction method forradiator selection which is suitable for high altitude regions.Firstly, based on previous studies, the dependence of thermophysical parameters ofair on altitude has been summarized, including density, kinematic viscosity coefficientand thermal diffusivity, etc.Secondly, the mathematical analytical solutions of flat radiator and electric radiatorhave been established. Since the geometric boundary conditions of ribbed radiator isvery complicated, numerical method based on finite difference method was used todiscretize the ribbed radiator heat transfer model. And the corresponding discreteequations for boundary nodes and inner nodes were established. In the modeling processof the three types of radiators, the thermal boundary conditions have been simplified.Also, trial method was applied in solving the models, as the equation involves manyparameters.Then, numerical simulation software COMSOL Multiphysics based on finiteelement method was used to build numerical simulation models for the three types ofradiators. Meanwhile, a field test of wall-hanging stove+radiator system located inLhasa has been conducted. The numerical results, experimental data and theoreticalcalculations were compared with each other, and the relative errors obtained are lessthan20%, which verifies the correctness of the theoretical model.Finally, the key factors affecting radiator heat transfer were analyzed and a conclusion was drawn: the heat transfer coefficients of both flat radiator and ribbedradiator decrease with growing altitude, and heat transfer coefficient decreases1.5%-2.5%for500m increase of altitude; the limit value of heat emission per unit area ofcylindrical electric radiator also decreases with growing altitude, with an attenuation of1%-1.5%for500m increase of altitude. In addition, with the results of a large numberof calculations, correction coefficients for flat and ribbed radiators have been fitted intopolynomials.