Design Self-Regulating Heating Cables
As the pipes are heat traced by self-regulating heating cables (when self-regulating heating heat tracing the pipe), if confirm its power, nodal distance and length of cables, desired pipe maintenance temperature Tm, minimum expected ambient temperature Ta, pipe size, the type and thickness of heat preservation.
一、Calculate heat dissipating capacity of pipe.
1. Calculate temperature difference of Tm and Ta : △T= Tm-Ta
2. Use chart 1 to determine heat preservation Coefficient Ki.
3. Use chart 2 to determine heat loss Coefficient Qa. Indoor is QaX0.9.
4. Pipe heat dissipating capacity Qp=△TX Ki X Qa.
二、Confirm the power of self-regulating heating cables.
Get the output power Qh of self-regulating heating cables from power-temperature Chart, Qh should be more than or equal to heat loss Qp pipes, and for nonmetal pipes is QhX7.
Sometimes use the self-regulating heating cables which output power less than pipe’s heat loss also could get approving result. This case, the cable should spiral-enlace on pipes. Following calculate the nodal distance and length:
1. Calculate power enlarge Coefficient Rp=Qp/Qh
2. Confirm the distance。
3. Confirm the distance of cable Lh=LpXRp(Lp is the length of pipes)
三、The common heat preservation Coefficient (chart 1)
|
Heat Preservation Material |
Heat Preservation Coefficient |
|
Fiberglass |
1.00 |
Perlite |
1.29 |
|
Calcium Silicate |
1.48 |
Polystyrene Foam |
1.48 |
|
Polyurethane Foam |
0.67 |
Polyurethane Foam |
1.90 |
|
Foam rubber(foam) |
1.19 |
四、Heat loss Coefficient Qa of pipes(W/m°C)(Chart 2):
|
Common size (in) |
Thickness of heat preservation |
|
15 |
25 |
40 |
50 |
65 |
75 |
100 |
|
1/2 |
0.30 |
0.24 |
0.18 |
0.18 |
- |
- |
- |
|
3/4 |
0.35 |
0.24 |
0.18 |
0.18 |
- |
- |
- |
|
1 |
0.41 |
0.30 |
0.24 |
0.18 |
0.18 |
|
|
|
1-1/2 |
0.53 |
0.35 |
0.24 |
0.24 |
0.18 |
|
|
|
2 |
0.65 |
0.41 |
0.30 |
0.24 |
0.24 |
- |
- |
|
2-1/2 |
0.77 |
0.47 |
0.35 |
0.30 |
0.24 |
- |
- |
|
3 |
0.95 |
0.53 |
0.41 |
0.30 |
0.30 |
- |
- |
|
3-1/2 |
1.06 |
0.59 |
0.41 |
0.35 |
0.30 |
0.30 |
- |
|
4 |
1.18 |
0.65 |
0.47 |
0.35 |
0.35 |
0.30 |
0.24 |
|
6 |
1.65 |
0.89 |
0.65 |
0.53 |
0.41 |
0.35 |
0.30 |
|
8 |
2.07 |
1.12 |
0.77 |
0.59 |
0.53 |
0.47 |
0.35 |
|
10 |
2.60 |
1.36 |
0.95 |
0.77 |
0.59 |
0.53 |
0.41 |
|
12 |
3.01 |
1.60 |
1.12 |
0.83 |
0.71 |
0.59 |
0.47 |
|
14 |
3.31 |
1.71 |
1.18 |
0.95 |
0.77 |
0.65 |
0.53 |
|
16 |
3.78 |
1.95 |
1.34 |
1.06 |
0.89 |
0.71 |
0.59 |
|
18 |
4.20 |
2.19 |
1.48 |
1.18 |
0.95 |
0.83 |
0.65 |
|
20 |
4.67 |
2.42 |
1.65 |
1.24 |
1.06 |
0.89 |
0.71 |
|
24 |
5.56 |
2.84 |
1.95 |
1.48 |
1.24 |
1.06 |
0.83 | | 
