Research About Heat Transfer Problem In Operations Of Floor Heating

As a new heating of energy-efficient and comfortable, low-temperature hot waterheating system of floor radiation is increasingly applied to a wide range of housingconstruction. Domestic and foreign scientists and engineers carried on a large number ofresearches about its heating mechanisms, thermal comfort and energy-saving effect areas. Butmost research focused on the internal structure of the floors and heat transfer process, fromthe simulation calculation of heat transfer model established the internal floor, analyses coverthickness, and pipe distance, laying way and other factors for the system temperaturedistribution. As for the regulation and control of the floor heating radiation involved is less.Because radiation floor cover has capability of strong store heat and exothermic, the use ofintermittent adjustment is more superiority and very suitable for civilian residential. Mostresearchers are still under way of rough quality and flow regulation accord with regulate thetraditional radiator, ignores the structure of the thermal inertia floor heating, it is clear thatregulation ways on the one hand, will affect residents comfortable, on the other hand willcause great waste of energy. Some researchers neglect thermal capacity indoor air in thefoundation process, and finally led to the calculation results inconsistent. Thus, it need furtherstudy for floor heating systems intermittent operation to establish more realistic heat transfermodel, summed up the law of temperature changes and provide a theoretical basis andpractice guidance for intermittent operation.The major work done by the paper as the following:(1) By using the heat transfer theory, established dynamic heat transfer model forradiation heating room floor. The mathematical models are separated following the limiteddifferential law and develop calculation procedures by Visual Basic applications.Calculation procedures working for two typical examples, simulation calculations resultshows that â‘  In preheat phase, different ground floor temperature changes largely underthe same conditions, in this calculation, the temperature difference after preheat is 10degrees between marble and marble-blankets ground, and the marble surface changes morequickly. â‘¡ Under the he same conditions, room temperature in heat preservation wall is3-5 degrees more than ordinary wall and more energy-efficient â‘¢ Temperature in heatingroom outdoor in North will be divided into several small phase, through lots of simulationcalculation, it recommended best intermittent operation project for the temperature changefor each stage.(2) In order to test heat transfer models and calculations reliability, measured for ofthe actual floor radiation room temperature fields, 74 thermocouple temperature points wasdesigned respectively in the floor surface, wall structure inside surface and interior layout,totally test for five days, continuous operation phase for former three days, intermittentoperational phase for latter after two days, compared the calculation with the test data, theresults show that in stable calculation, the result of errors in the various parts are within 1.5degrees, in unstable calculation, the error of the indoor temperature and floor surfacetemperature are within 1.5 degrees, error internal wall is within 2.5 degrees, the temperaturechanges law are basically the same. Measured results also confirmed that it is appear of a"head and cool feet warm" in the radiation room floor system in the high direction, as anegative temperature gradient distribution, a slight temperature rise close to the ceiling.Temperature changes less and has a moderate tendency in intermittent operation process, itfurther confirmed that it is appropriate to this operation for floor heating system.(3) Using of PMV -PPD index, when people wearing clothes of different thickness,give hot room environment evaluated respectively to the floor heating and the traditionalradiator heating room. The results showed that man feel most comfortable in the floorheating room when he wearing thin sweater knitted wool trouser, and only 7 percent ofthose who dissatisfied. Introducing the concept of efficiency, worked by the calculation, itcan be known that low-temperature floor heating system in the radiation of heat integrated,on the "quality" and "quantity" basis, can be conserved for energy about 75 percent whencompared with ordinary radiator heating system.(4) Using the present and yearly cost index for the economic evaluation and economicanalysis of floor heating radiator heating, the results showed that either consider ofeconomic benefits, or the social context, floors radiation heating is feasible project and hasgreat advantages in comparison with the radiator traditional heating system.From the theory research and on-site tests of the floor heating system radiationintermittently operational in this paper, it provides a theoretical basis for operation controland popularity of floor radiation heating method, It will become truly energy-efficient,comfortable ideal heating system and have a certain academic and application value.