Water Flow Rate and Pipe Diameter Calculation

Water flow rate and pipe diameter are explored in detail the accounts. Hot-water heating systems, individual and regional residential heating today, factory and workshop, greenhouse heating, geothermal energy is used for heating systems.

Water Flow Account

Heating system needed water flow, heating system pipe dimensioning of the system (determination of the pipe diameter) is the first parameter to the need-to-know basis. Being in the fluid velocity, pressure drop, as well as other parameters is detected, tube diameter can be specified. Water flow, heating system heat and return water temperatures are specified is calculated from Equation 1.1 ;
m = Q/(ρ × Cp × ΔT) [m³/h] Equation 1.1
here;

m [m3/s]: Water flow rate
Q [kW]: thermal requirement
ρ [kg/m3]: Water density (Table 1.1)
CP [kJ/kg ° c]: specific Water temperature (Table 1.1)
ΔT [° c]: return pipe temperature difference between
Example-1.:
Heating needs 1000 kW, heating system going temperature 90 ° c and heating return temperature of 70 ° c is a greenhouse heating water requirement;
m = 1000/(972 × 4198 × 20) = 0.0123 [m³/h] = ‘ 0,0123 × 3600 = 44.1 [m³/h]
Note: the density and specific heat of Water round trip average temperature (80 ° c) values are found from Table 1.1.

Pipe Diameter Calculation

Heating system needed water flow has been calculated following determination of the pipe diameter that make up the system after the calculation is appointed by following the steps.
Bernoulli’s principle, the stream can occur for A case in point, B Point must have more energy.(Figure 1.1) This energy difference, pipe friction between the fluid and the pipe inner towers used to defeat the resistance.

Figure 1.1 – Bernoulli’s principle

Total energy exchange fluid pressure drop hf (m). Pressure drop depends on the following parameters.
L [m]: Pipe length
D [m]: pipe inside diameter
V [m/s]: being in the average fluid velocity
μ [Pa s]: Fluid dynamic viscosity
ρ [kg/m3]: Fluid density
KS [m]: Pipe roughness
Pressure drop created fluid resistance, D’Arcy-Weisbach Equation is known as the Equation 1.2 is calculated from.
HF = λ × (L/D) × [(ρ. V ²)/2] [Pa] Equation 1.2
here;

HF [Pa]: Pressure drop
λ [-]: coefficient of friction (Moody diagram in Figure 1.2)
L [m]: Pipe length
D [m]: pipe inside diameter
V [m/s]: being in the average fluid velocity (Equation 1.3)
ρ [kg/m3]: Fluid density
Pipe diameter calculation, Equation 1.2 is done through the use of the form of the trial-and-error Method. Fluid flow rate approximately according to the pipe diameter selected; selected pipe diameter and other parameters, Equation 1.2 sets out instead. Pipe length, L, rather than 1, bring in a pipe fluid meter pressure drop is calculated. Heating systems, recommended pressure drop a pipe with a mistress for small diameter pipes (from DN150 tubes) for 100-200 Pa/m, and large-diameter pipes for 100-150 Pa/m. bring pressure drop of pipe diameter Selected, must remain within the range of the recommended pressure drops. If the pressure drop occurring according to the selected anchor recommended is not selected in the range of diameters by changing the pressure drops calculations in this range is again until.
Being in the fluid speed is calculated from Equation 1.3 .
V = (4 × m)/(π × D ²) [m/s] Equation 1.3

here; V [m/s]: being in the average fluid velocity
m [m3/s]: Water flow rate (Equation 1.1)
D [m]: pipe inside diameter

Figure 1.2 Moody Diagram
Calculation of calculation of pipe diameter and pressure drops, relative roughness, Reynolds number, the calculation of dynamic viscosity of the fluid as well as other required parameterExample-1.2 are described, too.

Example-1.2:
Heating water needs 45 [m³/h] is the greenhouse heating system pipe diameter? (The average water temperature 80 ° c)

1. Iteration (pipe diameter = DN150, D = 160, 3 mm)
• Being in the fluid speed is calculated from Equation 1.3 .

V = (4 × 45)/(π × 3600 × 0,1603 ²) = .62 [m/s]
• Coefficient of Reynolds is based on the number of Reynolds number is calculated from Equation 1.4

Re = ρ × V × D/μ [-] Equation 1.4

here;
Re [-]: Reynolds Number
ρ [kg/m3]: Fluid density (Table 1.1)
V [m/s]: being in the average fluid velocity (Equation 1.3)
D [m]: pipe inside diameter
μ [Pa s]: dynamic viscosity of water (Table 1.1)

Table 1.1 – water’s Thermal Properties
From Equation 1.4;

Re = 971,82 × .62 × 0,1603/(0,355 × 10-³) = 272071 [-]

• The relative coefficient of friction pürüzlülüğe dependent relative roughness is calculated fromEquation 1.5 .

B. Roughness = ks/D [-] Equation 1.5

here;
KS [m]: Pipe roughness (Table 1.2)
D [m]: pipe inside diameter


Table 1.2 – according to the roughness coefficients in Material

Equation 1.5 den;
B. Roughness = 0.045 * 10-³/0.1603 = 0.0003 [-]

• Coefficient of friction, the Reynolds number (272071), and relative pürüzlülüğe (0.0003) from Figure 1.2 λ = 0.016.

• All these values are found in Equation 1.2 is calculated by pressure drop instead.

HF = 0.016 × (1/0,1603) × (971.82 × ² 0,62/2) = 18.64 [Pa/m]

Pressure drop, from the recommended pressure drops (100-150 Pa/m) is very low and smaller than the diameter of the above account for the digits that is repeated until a value within the range of the pressure drop.

2. Iteration (pipe diameter = DN100, D = 107, 1 mm)

V = (4 × 45)/(π × 3600 × 0,1071 ²) = 1.39 [m/s]
Re = 1.39 × 971,82 × 0,1071/(0,355 × 10-³) = 407532 [-]
B. Roughness = 0.045 * 10-³/0.1071 = 0.0004 [-]

• Coefficient of friction, the Reynolds number (407532), and relative pürüzlülüğe (0.0004) from Figure 1.2 λ = 0.016.

HF = 0.016 × (1/0,1071) × (971.82 × 1.39 ²/2) = 140.25 [Pa/m]

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