Precautions for the purchase of electronic radiator

About the price of radiator
The final transaction price of the radiator is related to the specification, model, quantity, delivery method and payment method of the selected radiator. It is necessary for the user to pay special attention to the fact that the aluminum radiator is usually made of pure aluminum or 6063 alloy, and the two materials have good thermal conductivity, which is several times higher than the thermal conductivity of miscellaneous aluminum. (see [relevant data] for its thermal conductivity.) because of the cost of the radiator More than half of the cost is material cost, and the price of miscellaneous aluminum is low; therefore, when purchasing a particularly cheap radiator, the loss of heat dissipation performance caused by the material should be considered.
First of all, determine the electronic components to be cooled, define their working parameters, working conditions, size, installation mode, and select the size of the base plate of the radiator slightly larger than the installation surface of the components. Because of the limitation of the installation space, the radiator mainly relies on the convection with the air to dissipate the heat, and the radiator beyond the contact surface with the components, its heat dissipation effect increases with the distance from the components And decline. For the single rib radiator, if the width of the required radiator is vacant in the table, you can choose to cut the radiator with twice or three times the width.
Calculation method of radiator selection
Heat dissipation calculation formula:
Rtf =(Tj-Ta)／Pc - Rtj -Rtc
The heat resistance RFF of radiator is the main basis for choosing radiator. TJ and RTJ are the parameters provided by semiconductor devices and PC is the parameters required by design. RTC can be found in thermal design books.
(1) Calculated total thermal resistance Rt: RT = (Tjmax TA) / PC
(2) Calculate the heat resistance RTF or temperature rise Δ TFA of radiator: RTF = rt-rtj-rtc Δ TFA = RTF × PC
(3) Determine radiator: according to the working conditions of radiator (natural cooling or forced air cooling), select the radiator according to RTF or Δ TFA and PC, check the heat dissipation curve of the selected radiator (RTF curve or Δ TFA line). When the value found on the curve is less than the calculated value, the appropriate radiator is found.
For profile radiator, when the thermal resistance curve or temperature rise curve cannot be found, it can be determined as follows:
Calculate the radiator temperature rise Δ TFA according to the above formula, and then calculate the comprehensive heat transfer coefficient α of the radiator:
α＝7.2ψ1ψ2ψ3{√√ [(Tf-Ta)／20]}
Where:
ψ 1 -- describe the influence of radiator L / B on α, (L is the length of radiator, B is the distance between two ribs);
ψ 2 -- describe the influence of radiator H / B on α, (H is the height of radiator rib);
ψ 3 -- describe the influence of radiator width W on α;
√ [(TF TA) / 20] - describe the effect of the highest surface temperature of the radiator on the temperature rise of the surrounding environment on α;
The above parameters can be found in the table.
Calculate the power Q0 of the surface between two fins
q0 =α×ΔTfa×（2h+b）×L
According to the number of fins n of single-sided or double-sided ribbed radiator, calculate the heat dissipation power PC ′
Single rib: PC ′ = nq0
Double sided rib: PC ′ = 2nq0
If PC ′ > PC, it can meet the requirements.
Parameter definition:
RT -- total internal resistance, ℃ / W;
RTJ -- internal thermal resistance of semiconductor device, ℃ / W;
RTC -- interface thermal resistance between semiconductor device and radiator, ℃ / W;
RTF -- heat resistance of radiator, ℃ / W;
TJ -- junction temperature of semiconductor device, ℃;
TC -- shell temperature of semiconductor device, ℃;
TF -- radiator temperature, ℃;
Ta -- ambient temperature, ℃;
PC -- operating power of semiconductor device, W;
Δ TFA -- radiator temperature rise, ℃;