Selection and calculation method of telecom cabinet air conditione
Formula:
Q t = (Q i + Q r ) ×1.2
Q t: Heat released by the cabinet (W)
Q i: Heat released by the inner cabinet (W)
Q r: Heat spreads from outside to the inside of cabinet (W)
Q i: Heat released by the inside of the cabinet (W)
The calculation of the heat released by the components in the cabinet is based on the following (related to the components installation).
1) Heating of variable-frequency drive, transformer, drive and servo amplifier etc.: rated power 1K, about 30~50W heat (depending on the load and divided by fan pump load and mechanical load).
2）PLC is about 35~50W heating(group as a unit), heat of industrial personal computer is controlled by its size. All calculated of 300W/ unit;
3）Heat of contact components: rated power1KW is about 5~20W heat, can be ignored compared with large power components.
4）Heat of common server is about 280-500W. Heat of UPS is 20% of its power.
E.g. When the variable-frequency drive is working with load, its loss (transformed into heating) is about 3%~5% of system rated power, which can be calculated. When the variable-frequency drive is of 1KW, the loss maybe 30W to 50W.
5）Heat of SCR:2W/A. 1KW DC Drive is about 7W~10W.
Q r =k×A×Δ T
k—Heat transfer coefficient
1)k=5.5W/ m2 .K Steel cabinet
2) k=12.0W/ m2 .K Aluminum-magnesium alloy enclosure
3) k=0.2W/ m2 .K Plastic material cabinet
A —Surface area of the cabinet（unit—m2 ）
Δ T=T 1 – T 2 （unit—℃）
T 1—maximum temperature of outside cabinet
T 2—controlled temperature of inside cabinet
E.g. Dimension of a steel cabinet: L×H×D：1500×2000×800 mm,
Heat of the inside elements is 1000W,controlled temperature inside the cabinet is 28 ℃, outside temperature is 35 ℃ 。
Answer. Surface area of the cabinet—A=1.5×2×2+0.8×2×2+ 1.5×0.8=10.4 m2.
Heat rumored from out to inside of cabinet—Q r = k ×A×Δ T = 5.5×10.4×（ 35-28 ） =400.4W
Total heat produced by the cabinet—Q t =( Q i + Q r ) ×1.2=(1000+400.4) ×1.2=1680.48 W
So choose the cabinet air conditioner with cooling capacity of 2000W.
