Heat transfer calculation for heat exchangers
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Calculations are performed for heat exchange of air through the radiator; water flows inside the radiator, and a heat pump supplies heat to it. In fact, it is also the radiator that calculates the heat dissipation amount. Calculation of heat exchange between hot water and cold air. For example: the temperature of the hot water flowing through the radiator is 40 degrees at the inlet, and it drops to 10 degrees at the outlet; the temperature of the incoming air is -10 degrees, and after passing through the radiator it rises to 10 degrees. Determine the heat exchange amount. The flow velocity of hot water in the radiator is 0.07 m/s. Or, calculations of how much heat is needed to raise the temperature from -10 degrees to 15 degrees after cold air passes through a radiator, and what temperature the water entering the radiator should be. Those who are experts in this area, please contact me at 13061371315; there will be a reward!
Your question relates to heat transfer principles and calculations, which involve specialized knowledge such as thermodynamics and fluid dynamics. The formula for calculating the heat transfer amount is: Q=mcΔT, where Q represents the heat, m is the mass, c is the specific heat capacity, and ΔT is the temperature difference. For example, regarding the first problem you mentioned: “The temperature of the hot water entering the radiator is 40 degrees, while the outlet water temperature is 10 degrees. The temperature of the incoming air is -10 degrees; after passing through the radiator, the air temperature rises to 10 degrees. Calculate the amount of heat exchanged.” ”To perform the calculation, it is also necessary to know the mass or volume of water and air. The second question: To raise the temperature from -10 degrees to 15 degrees after the cold air passes through the radiator, how much heat is required, and what temperature should the water entering the radiator have? ”To perform the calculations, it is also necessary to know the mass or volume of air, as well as the performance parameters of the radiator. It is recommended that you consult professional engineers specializing in thermodynamics or heat exchange equipment; they can provide more accurate calculations and recommendations. I’m sorry, as an AI, I’m unable to conduct phone calls. If you have any other related questions, feel free to ask them here. .
As the friend on the second floor said, the topic posed by the original poster lacks the necessary conditions and is therefore unsolvable. Here, a reference value of 1 is provided from the perspective of thermal equilibrium. For the first question, in order for both air and water to meet the required inlet and outlet temperatures, air with a flow rate of 1000 kg/h can supply water with a flow rate of 160 kg/h. The heat requirement is approximately 5.53 KW; the poster can estimate this value based on the flow rate ratio. As for the second question, for an air flow rate of 1000 kg/h, the heat required to achieve the desired temperature rise at the inlet and outlet is about 6.9 KW. However, since the necessary conditions are lacking, there can be countless possible solutions regarding the temperature of the water that needs to be used. For example, to maintain the same water volume and outlet temperature as in Question 1, the inlet water temperature is 47.53℃
This post was last edited by breath on 2023-8-28 at 10:21. Air-type heat exchangers also fall under a very broad category. Due to the low heat transfer coefficient on the air side (the overall heat transfer coefficient generally does not exceed 30 W/m2/°C), finned tubes are usually chosen; the selection of heat transfer methods requires consideration of the finned tube structure in the calculations.
Students? The questions asked are the most basic and simple ones: how is the heat transfer calculated? Q=mcΔT, where Q represents heat, m is mass, c is specific heat capacity, and ΔT is the temperature difference. Another question relates to thermal equilibrium – the amount of heat that needs to be supplied on one side depends on the degree of heating on that side. Don’t teachers teach these basic things? It’s still a matter of calculating the heat transfer amount. The tricky part of calculating the heat transfer rate is having to look up the physical properties of the medium.
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Heat balance equation: Q_release = Q_absorption (unit: W). Heat load: Q = C × M × ΔT, where: C is the specific heat capacity of the cold (or hot) medium, in J/(kg×K); M is the mass flow rate of the cold (or hot) medium, in kg/h or kg/s; ΔT is the temperature difference between the inlet and outlet of the cold (or hot) medium, in °C. Various correction factors are then calculated based on the properties of the cold and hot media as well as the structural characteristics of the heat exchanger. Finally, the heat exchange area is determined using the formula: Q = K × A × Δtm. Where: K------total heat transfer coefficient, W/(m^2×℃); A------heat exchange area, m^2; Δtm---effective average temperature difference, ℃. Finally, the strength of the equipment and vibration conditions are checked; if this step is not passed, then it is necessary to start over from the selection of the heat exchanger. Reference: Appendix B of GB/T 151-2014