Selection Calculations: For Cooling Fans; Heater Selection Example

In order to maintain the appropriate temperature inside equipment, it is necessary to know the required heat generation of the heater to meet the conditions.
The required heating generation can be obtained from the size and material of the equipment, and the temperature inside and outside the equipment. Here is the description of a selection example of the most suitable heater for your equipment.

Flow Chart for Heater Selection

Calculation Method for Selection

Follow the flow chart to calculate based on the conditions.
(1) Verification and calculation of operating conditions and equipment specifications
For example, select a heater to set the interior of the equipment installed in a general factory in a cold region to the target temperature.

• In regions where the minimum temperature reaches -20 °C during the winter months
• The operating ambient temperature of devices inside the equipment is 0 to 50 °C
• Set the target temperature inside the equipment to 5 °C

① Check the Specifications of the Equipment

Item	Specifications
Equipment size (material: iron)	Width (W) = 0.7 m Height (H) = 1.0 m Depth (D) = 0.4 m
Temperature conditions	Target temperature T1 = 5 °C Ambient temperature T2 = −20 °C
Heat Generation Inside the Equipment*	Q = 100 W
Power supply	50 Hz 100 V

• *The heat generation from devices inside the equipment. Consider if there is a heat source other than the heater, such as a power supply, inverter, or programmable controller.
  

② Calculate the Values Required for Selection

• Calculate the effective surface area of the equipment (heat radiation area) S
  The method for calculating the effective surface area of the equipment is as follows:

Here, we assume that the entire perimeter of the equipment is open.

Effective surface area S of the equipment

1.4 × W · D ＋ 1.8 × D · H ＋ 1.8 × W · H

1.4 × 0.7 × 0.4 + 1.8 × 0.4 × 1.0 + 1.8 × 0.7 × 1.0

2.37 [m²]

• Calculate the temperature difference between the target temperature and the ambient temperature

Temperature Difference ΔT

T₁ − T₂

5 − (−20)

25 [°C]

(2) Calculating the heat generation that satisfies the conditions
Here, both the method of calculation and a simplified method using graphs are explained.

How to Determine by Calculation

Q_H

S × 5^* × ΔT − Q

2.37 × 5 × 25 − 100

196.25 [W]

• *If the material of the equipment is iron, the overall heat transfer coefficient will be 5.
  Materials and overall heat transfer coefficients for other equipment are as follows:
  Stainless steel: 4.5; Aluminum: 12.0; and Aluminum (2 layers): 4.5

How to Determine by Graph (Figure Below: Heating performance graph)

①

Find the intersection point A of the effective surface area (S) of 2.37 m² and the temperature difference (ΔT) of 25 °C.

②

Draw a line parallel to the horizontal axis, starting from the intersection point A.

③

The required heat generation (Q_H') of 300 W can be obtained from the intersection point of the parallel line and the vertical axis.

④

The heat generation (Q) inside the equipment is excluded from the required heat generation (Q_H'), because it is used as a heat source like a heater during operation.

Q_H

Q_H' − Q

300 − 100

200 [W]

(3) Selecting the Best Heater
Result from calculation: 196.25 [W]
Result from graph: 200 [W].
From the calculation results, we can see that 200 W heat generation is required.
Based on the required conditions, select the HMA200F-1, which is a single-phase 100 VAC specification.

Introduction to Thermostats

We recommend the use of the AM2-XB1 thermostat for heater, which contributes to energy savings when used in conjunction with heating modules.
Click here for details.