Basic Theory of the Car Radiator
1. Heat conduction of car radiator
There are three heat conduction methods for the heat conduction of car radiators , namely heat conduction, convection and radiation. Among them, the relationship between thermal radiation and temperature is very close, and under normal circumstances, the temperature of the thermal fluid of the vehicle radiator is not high, and the thermal radiation is limited. Therefore, we usually do not consider heat radiation when designing.
The law of heat conduction phenomenon is summarized as Fourier's law. That is, Q=-λf(dt/dx). In the formula, λ is the proportional coefficient, called thermal conductivity, and the negative sign indicates that the direction of heat transfer is opposite to the direction of temperature rise. The basic calculation of convective heat transfer is the Newtonian cooling formula, that is, Q=α(tg-td), where α is the convective heat transfer coefficient, tg is the temperature of the high-temperature fluid, and td is the temperature of the low-temperature fluid.
2. The "secondary heat transfer theory" of the car radiator
The theory of the partition wall type vehicle radiator is the "secondary heat transfer theory". Let's take a car water tank as an example to illustrate. The so-called "secondary heat exchange" means that the first heat exchange is the heat exchange of the cooling water to the inner wall of the radiating tube of the vehicle radiator, and the second heat exchange is the heat exchange from the outer wall of the radiating tube and the radiating belt to the air. It is not difficult to understand that the two heat exchanges are stable heat flows, that is, the heat exchanged by the two heat exchanges is the same. There is also a heat conduction in the middle, that is, the heat transfer from the inner wall of the radiating tube to the outer wall of the radiating tube, and the heat conduction from the inner wall of the radiating tube to the radiating belt. Through the analysis of the heat transfer process of the car radiator, it can be seen that the heat dissipation of the car radiator should be analyzed by the heat transfer process of the series system. The law is summarized as the following formula: Q=KF⊿T, where K is the heat release coefficient of the car radiator, F is the heat dissipation area, and ⊿T is the temperature difference. For the radiator, take the cold air side as the benchmark.
The above formula is just one of the simplest examples, that is, assuming that the tablet is taken as the research object. In fact, the vehicle radiator is not a simple flat plate. But the principle is the same. It is nothing more than adding a coefficient of area before its heat release coefficient.