[China Aluminum Industry Network] The experimental conditions and contents of this article This experiment is to test in the actual room. The difference from the radiator test standard is that the room temperature in the experiment varies with the outdoor weather conditions and the heat sink configuration and the water supply temperature and flow rate. The collected data includes the supply and return water temperatures, room temperature and flow rate, and the temperature is collected through a platinum resistance sensor. Flow measurement through a turbine flow meter (precision 3 series).
Under the experimental conditions, a series of tests were conducted on an aluminum radiator under constant and variable flow conditions to obtain the relationship between the heat dissipation and the calculated temperature difference. Through the analysis of experimental data, the heat characteristics of the radiator were performed. More in-depth research. This type of heat sink is a hood type LLD aluminum tube aluminum string radiator manufactured by Tianjin Tailai HVAC Equipment Co., Ltd. The experiment was conducted mainly in consideration of its small thermal inertia, rapid temperature rise and internal cleanliness. It is not easy to block the pipeline, and it is more suitable for the use of heat metering variable flow systems.
Radiator thermal characteristics analysis The following analysis of LLD type aluminum convection radiator variable flow and constant flow test: ltnLLD type aluminum convection radiator 50kglh constant flow test results Operating conditions Water supply temperature °C Flow k å» Water temperature difference °C Calculation of temperature difference °C heat dissipation W15.lmLLD type aluminum convection radiator 150kg/h constant flow test result condition water supply temperature °C flow rate knob supply water temperature difference °C calculated temperature difference °C heat dissipation W155.lmLLD type aluminum convection radiator variable flow test results Operating conditions Water supply Temperature °C Flow kg/h Temperature difference of return water °C Calculation of temperature difference °C Heat dissipation Wl85.4 InLLD type aluminum convection radiator 150kg/h Constant flow test result Condition Supply temperature °C Flow kg/h Supply water temperature difference °C Calculation Temperature difference °C heat dissipation W155.
As can be seen from the fitted function formula, under different flow conditions, the heat dissipation of the radiator varies with the flow rate. When the flow rate is low, the heat dissipation of the radiator changes more significantly. This is determined by the thermal characteristics of the heat sink, and the smaller heat sink flow rate also means that the heat dissipation increases with the tunability of the flow. Therefore, compared with the single pipe system, the double pipe system has a large temperature difference between the inlet and the outlet of each radiator, and the relationship between the heat dissipation amount of the radiator and the water quantity is sensitive and the tunability is better.
The curve obtained for a small fixed flow of 15 kWg is compared with the curve obtained by the variable flow test, and the two are relatively close. The heat transfer experimental formula fitted by the two test results is not much different. As can be seen, under the two conditions, the difference in heat dissipation is small. As the calculated temperature difference increases, the difference between the two becomes smaller and smaller. In variable flow conditions, the water supply temperature is constant, and the flow through the radiator increases, resulting in an increase in the calculated temperature difference. The conclusion of this experiment further shows that under the condition of large flow rate, the heat sink calculation formula obtained under the standard operating conditions of fixed flow rate is still applicable to the variable flow system, but when the flow rate is small (if the heat metering is implemented, the user's attention Economic benefits are associated with it. When users go to work or go out, they will close the temperature control valve to a very small value. At this time, the flow through the radiator should consider revising the original formula.
At present, the widely-operated heating system simplifies initial adjustment or lacks necessary control measures, resulting in the pipe network system being in a state of large flow and small temperature difference that deviates from the design state. To a certain extent, this can solve the problem of remote failure of the remote users at room temperature due to hydraulic imbalance. The problem, but the implementation of heat metering, this way of operation has created a big drawback.
Large flow, small temperature difference operation is based on the basic principle that when the flow rate is more than 2 to 3 times of the design flow rate, the heat dissipation amount is no longer sensitive to the flow rate change.
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