What is a closed loop heat exchanger? Under what circumstances is it used?

The closed-loop heat exchanger uses external air to cool the air in the control cabinet, but the two parts of the air are not in direct contact, and isolating the internal and external airflow channels can prevent dust and moisture from entering the control cabinet from the outside. Closed loop heat exchangers are made of rugged materials and are designed to be produced without pollution.

The heat exchanger can be used when the maximum temperature allowed in the control cabinet is higher than the maximum temperature outside. Based on the principle of heat exchange, the control cabinet can be placed in harmful external environments, such as salt-rich air. The internal circulation of air can maintain a relatively stable temperature in the control cabinet, without being affected by the external air flow. When the demand for refrigeration increases, the flow rate can be increased. The first limitation is the size and noise of the fan. The cooling capacity of a heat exchanger depends on the temperature difference between the two parts of the air flow, the flow rate, the design of the different and the size of the size. The heat exchanger can be placed at ambient temperatures above 45 ° C, and the closed-loop heat exchanger can be securely mounted on the control cabinet.

Heat exchangers typically use DC fans, which allow emergency backup batteries to be activated in the event of a loss of AC power, and this cooling can be combined with refrigeration systems for a more reliable solution.

Reasons to use electric cabinet heaters
The heat generated by the electrical equipment under load can prevent the accumulation of condensation, but when the equipment stops working and cools down, it will gradually adapt to the ambient temperature, so that the temperature in the cabinet drops below the dew point. So this triggers the demand for radiant heat! The heater inhibits condensate formation by raising the temperature of the electrical cabinet several degrees above the ambient temperature outside the cabinet.

■ Leizg H series heater covers the range from 10W to 10000W.

■ Rich heater equipment: temperature controller, humidity controller, pressure relief compensation device, etc.

Heater selection

Calculation prerequisite:

1. Size of electrical control cabinet (length, width, height)

2. As a rule, it is necessary to understand the location of the electrical control cabinet (e.g. single cabinet, row cabinet) and the effective surface area of the electrical cabinet

3. Heat exchange coefficient (W/m2K) of electric cabinet body material (e.g. metal, plastic)

4. The temperature difference between the set temperature Ti(oC) inside the cabinet and the temperature Tu(oC) outside the cabinet (e.g. : day-night, summer-winter, climate change) △T(K)

5. The heat emitted by the electrical equipment inside the cabinet (such as transformers, relays and frequency converters, etc.) during operation

Select parameters for calculation

1. Calculate the surface area of the electrical cabinet according to its dimensions

2. The position of the electric cabinet (as shown in the following figure) The formula for calculating the surface area of the electric cabinet is A(m2) (H height,W width,D depth).

A single perimeter open A=1.8×H×(W+D)+1.4×W×D

A single wall A=1.4×W×(H+D)+1.8×D×H

Front or rear unit in the cabinet, the rest of the empty A=1.4×D×(H+W)+1.8×W×H

Front or rear unit in the cabinet, against the wall A=1.4×H×(W+D)+1.4×W×D

Middle and middle unit in the cabinet, open at the back A=1.8×W×H+1.4×W×D+ D×H

The middle unit of the cabinet, against the wall A=1.4×W×(H+D) +D ×H

The middle unit of the cabinet is covered with A=1.4×W×H+0.7×W×D+ D×H against the wall

Example: The electric cabinet is open around 2000mm high /800mm wide /600mm deep, then A=1.8×2.0×(0.8+0.6)+1.4×0.8×0.6=5.712m2

3. Electric cabinet body material and heat transfer coefficient K (W/m2K)

4. Temperature difference between inside and outside the cabinet △T(K)

Painted steel 5.5W /m2K

Stainless steel plate 4.5W /m2K △T = Ti-Tu

Aluminum plate 12 W/m2K

Double structure aluminum plate 4.5W /m2K

Plastic board 3.5W /m2K

Formula for calculating the amount of heat required (heater)

Required heat P (W) = electrical cabinet surface area A (m2) × cabinet material heat transfer coefficient K (W/m2K) × temperature difference △T(K)

For example, W =5.712 m2 x 5.5 W/m2K x 15K=471.24W

Results: The heater with a calorific value of 500W is required to meet the requirements. If the electrical cabinet is located outdoors, the calorific value of the heater is doubled!

The necessity of cooling the electric cabinet

With the rapid acceleration of the process of human industrialization and the continuous improvement of the degree of automation of various equipment, well-made, high-precision equipment that continues to shrink in size, such as frequency converters, PLCS, module power supplies, etc., are being used more and more widely. When these devices work, they will generate a lot of heat, and these devices themselves are extremely sensitive to high temperature, and when they are in a high temperature state for a long time, it will seriously affect the stability and service life of the control equipment.

The usual solution is to install a fan on the control cabinet to achieve cooling, but when the fan is working, the dust, oil and harmful gases from the outside will also enter the control cabinet, and will be electrostatic adsorption on the surface of the circuit board, which will cause corrosion of the chip components and printed lines, and affect the heat dissipation of the components. The accumulated dust will also cause a short circuit in the high-pressure part of the circuit board after being damp. The longer the working time of the control cabinet, the more prominent the above problems, and the accumulation of a certain degree will cause sudden failure of the control part. And the cooling effect of the exhaust fan is not obvious, especially in the case of high temperature in summer, or when there is a heat source around the electrical cabinet, when the ambient temperature is higher than 35 ° C, only the exhaust fan can not solve the high temperature of the electrical components in the cabinet.

The air conditioner of the electric cabinet is to achieve heat absorption and cooling through compression refrigeration, so that the control cabinet in the closed case, the heat and water in the air in the control cabinet will be transferred to the outside of the cabinet. The high temperature, dust, oil, and corrosive gases in the external environment will not enter the inside of the control cabinet, thus solving a series of problems caused by fan heat dissipation. The control cabinet can always be maintained in the ideal temperature environment of 30-35 ° C, and the service life and stability of electronic and electrical equipment are effectively guaranteed.

The hardware damage caused by the sudden failure of the control system, and the economic and reputation loss caused by the delay of delivery caused by the shutdown are huge. The cost of installing the control cabinet air conditioner only accounts for a small part of the total amount of the whole equipment (set). The use of the control cabinet air conditioner plays an important role in the safe operation of the whole equipment and the extension of the service life of the control system.