MAINTAINING TEMPERATURE FOR DUCT

MAINTAINING TEMPERATURE FOR DUCT

If one needs to decide the power, reeling pitch and length of automatic-control-temperature heating cable when it maintains the temperature for the duct, the following items are necessaary: the maintaining temperature of the duct, the minimun ambient temperaturehe size of the duct, the matenal and thickness of the maintain-temperature layer

1. Difining the difference between maintaining temperature Tm and the minimun ambient temperature Ta: △T=Tm-Ta
2 Determine the thermal insulation material coeffcient Ki
3. Determine the heat loss coeficient Qa according to the pipe size and insulation thickness. If the pipe is indoors, the obtained healloss coefhcient shall be multiplied by 0 .9
4 Thermal loss ofthe duct Qp=T x Ki x Qa

The output power, Qh, of self-limited temperature heating cable choosing from the Thermal power-Temperature Curve should behigher than or equal to the loss of the duct heat, Qp, For non-metal duct, Qh in the curve should multiply 0.7.
In some occasions, using self-limited temperature heating tape which output power is lower than the calculating heat loss of the ductOp, can as well reach a satisfactory result. Under this circumstance, the cable should wind spiraly around the duct, calculation procedureof pitch and length as follow:
1.Calculating the extending power coefhcient, extending power coefhcient Rp=Qp ÷ Qh
2. Determing the pitch, according to the calculated value Rp and duct size, to determine the required pitch P
3. Determing the length, cable length Lh=Lp x Rp (Lp represent duct length)