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Δt – temperature difference, K or °C;
2
μ – absolute viscosity, kg/m·s or N·s/m .

 L 
Re  , (1.15)
v

where ω – velocity, m/s

L – characteristic dimension, m

2
ν – kinematic viscosity = μ/ρ, m /s

Table 3 – Natural Convention Correlation

Sample Problem Statement

A 6 kW heat transfer rate is needed for heating of apartment. It is planned to use a

horizontal pipe with 120 mm diameter, in which water moves with the temperature of

0
0
124 C. A temperature of the apartment is 24 C. Determine necessary length of pipe, if
2
convectional heat transfer coefficient is 11 W/(m K).

I
Q  q  F    F (t t - ), W
1 2

16