Heat Loss Calculation Method for Pipe

Pre-insulated pipes Heat Loss package in case of a mistress of the pipe directly buried pipes occurring heat loss is, f, is calculated from the following equation 2.1.

here;

f [W / m]: pre-insulated pipe 1 meter pack heat loss occurring in the pipes
[W / m ° C]: pre-insulated pipe thermal conductivity package (Equation 2.2)
t _f [C]: Fluid temperature
T _g [° C]: Soil temperature (the depth of the buried pipe)

Thermal conductivity coefficient of 2.2 is calculated as follows from Eq.

here;
[W / m ° C]: pre-insulated pipe thermal conductivity package
R _s [m ° C / W]: The service pipe thermal conductivity resistance (Equation 2.3)
R _PR [m ° C / W] is the thermal conductivity resistance of the insulating material (Equation 2.4)
R _{P [m} ° C / W]: the thermal conductivity resistance of the casing pipe (Equation 2.5)
R _g [m ° C / W]: the thermal conductivity of the soil resistance (Equation 2.6)

Thermal conduction resistance Equations 2.2 – 2.6 calculated from the following equation.

R _s, service pipe Thermal Conductivity Resistance

here;
R _s [m ° C / W]: The service pipe thermal conductivity resistance (Equation 2.3)
D _o [mm]: the outer diameter of the service pipe
D _i [mm] in the service pipe inner diameter
s _s [W / m ° C]: Service pipe thermal conductivity coefficient (Table 2.1)

Table 2.1 – Thermal Conductivity by Material Type

Figure 2.1 – Service and the Internal and External Diameter Pipe Case
R _PR, Resistance Thermal Conductivity of Insulation Materials

here;
R _PR [m ° C / W] is the thermal conductivity resistance of the insulating material (Equation 2.4)
D _o [mm]: the outer diameter of the service pipe
d _i [mm]: inner diameter of the casing pipe
s _PR [W / m ° C]: thermal conductivity of the insulation material

The maximum value of the polyurethane insulation in accordance with standard 0.033 [W / m ° C] d.Value of the polyurethane insulation materials used by isobutylene l _PR = 0.028 [W / m ° C] d.

R _PE, Sheath Pipe Thermal Conductivity Resistance

here;
R _{P [m} ° C / W]: the thermal conductivity resistance casing pipe
d _o [mm]: the outer diameter of the casing pipe
d _i [mm]: inner diameter of the casing pipe
l _{P [W} / m ° C]: the thermal conductivity of the casing pipe (s _PA = 0.43 for polyethylene pipes)

R _g, the thermal conductivity of soil resistance

here;
R _g [m ° C / W]: the thermal conductivity of soil resistance
d _o [mm]: the outer diameter of the casing pipe
Z [mm]: landfill height,

The service pipe in the center ground level to the measured filling height (Z _c) soil surface resistance (100mm) are added. Z = Z _c + 0.1m

l _g [W / m ° C]: the thermal conductivity of the soil (Table 2.2)

Soil properties can not be determined exactly in line _g = 2.0 [W / m ° C] can be taken.

Table 2.2 – Thermal Conductivity Soil

Heat loss in pipe-2.1 Example:

Heating water needs of 45 [m ³ / h] of the pipe diameter DN150 greenhouse heating systems and heating water flow temperature of 90 [C] d. Pre-insulated pipes in the heating system pack (insulated pipes or geothermal pipe) is used and the length of the line in 1000 [m] d. Accordingly, what is the temperature at the end of the line of Heat Loss in pipes and heating water pipe occurred in 1 meter?(Fill height 500 mm and depth of the buried pipes, soil temperature is 5 [C] d.)

Insulated pipe features:

D _o [mm] = 168.3
D _i [mm] = 160.3
d _o [mm] = 250.0
d _i [mm] = 242.2
L _S [W / m ° C] = 76
l _Pr [W / m ° C] = 0.028
l _{P [W} / m ° C] = 0.43
l _g [W / m ° C] = 1.70

Thermal conductivity resistance Equation 2.2 – Equation 2.6 is calculated by using the above values.

According to the insulation type, different temperatures and for various diameters buried pre-insulated pack heat losses occurring in one meter of pipe Table 2.3, Table 2.4 and Table 2.5 it is shown.

From the fluid temperature at the end of the line is calculated as follows Equation 2.7.

here;
T ₂ [° C]: the final temperature of the water
T ₁ [° C]: the initial temperature of the water
f [W / m]: pre-insulated pipe in pipes packet occurring in 1 meter Heat Loss
L [m]: Pipe length
m [m ³ / h]: Water flow
r [kg / ^m3]: the density of water (Table 1.1)
C _p [kJ / kg. ° C]: specific heat of water (Table 1.1)

From Equation 2.7;

* Series-1: Standard Type Polyurethane Insulation
Table 2.3 – Series-1 ‘by Square to the Pre-Insulated Pipe incoming packet Heat Loss

Heat Loss in Piping Design Values

s _s, the thermal conductivity of the service pipe = 76 [W / m ° C]
s _PR, thermal conductivity of insulation material = 0.028 [W / m ° C]
l _PE, the thermal conductivity of the casing pipe = 0.43 [W / m ° C]
l _g, the thermal conductivity of the soil = 2 [W / m ° C]
Z landfill height = 500 [mm]
t _g, Soil temperature (the depth of the buried pipe) = 5 [° C]

Table 2.4 – Series Pre-Insulated Pipe by the Heat Loss 2 Occurred

Heat Loss in Piping Design Values

s _s, the thermal conductivity of the service pipe = 76 [W / m ° C]
s _PR, thermal conductivity of insulation material = 0.028 [W / m ° C]
l _PE, the thermal conductivity of the casing pipe = 0.43 [W / m ° C]
l _g, the thermal conductivity of the soil = 2 [W / m ° C]
Z landfill height = 500 [mm]
t _g, Soil temperature (the depth of the buried pipe) = 5 [° C]

Table 2.5 – Pre-Insulated by Series-3 package Occurring Pipe Heat Loss

Heat Loss in Piping Design Values

s _s, the thermal conductivity of the service pipe = 76 [W / m ° C]
s _PR, thermal conductivity of insulation material = 0.028 [W / m ° C]
l _PE, the thermal conductivity of the casing pipe = 0.43 [W / m ° C]
l _g, the thermal conductivity of the soil = 2 [W / m ° C]
Z landfill height = 500 [mm]
t _g, Soil temperature (the depth of the buried pipe) = 5 [° C]

Source: Izobor, Heat Loss in pipes, izobor.com
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