Heat gain in buried chilled water pipes
Heat gain in buried chilled water pipes
(OP)
As per 2008 ASHRAE HANDBOOK CHAPTER 11, to determinate annual heat gain for a buried system the STEADY-STATE CALCULATIONS are appropriate.
can anybody tell me why in that formula it's not present the heat transfer by convention from the pipe to the chilled water? what they mean with this steady-state?
Rs={ln{(d/r0)+[(d/r0)^2 - 1]^1/2 } }/2 pi Ks
Rs = thermal resistence of soil
Ks = thermal conductivity of soil = 2.6 W/m K (as per ashrae for saturated soil)
d = burial depth to centerline of pipe= 1.87 m
r0 = outer radius of pipe = 0.62 m
Rp = {ln(r0/r1)}}/ 2 pi Kp (negligible)
Ri = {ln(r2/r0)}}/2 pi Ki
Rp = thermal resistence of pipe (negligible)
Ri = thermal resistence of insulation
r1 = internal radius of pipe = 0.6 m
r2 = outer radius of insulation = 0.67 m
Kp = thermal conductivity of pipe (negligible)
Ki = thermal conductivity of insulation = = 0.026 W/m K (polyurethane foam)
Rt = total thermal resistence = Ri + Rs
q = (Ts-Tf)/Rt
q = total heat gain W/m
Ts = average annual soil Temp. = 30 deg. Celsius
Tf = fluid Temp. = 5 deg. Celsius
any help please
can anybody tell me why in that formula it's not present the heat transfer by convention from the pipe to the chilled water? what they mean with this steady-state?
Rs={ln{(d/r0)+[(d/r0)^2 - 1]^1/2 } }/2 pi Ks
Rs = thermal resistence of soil
Ks = thermal conductivity of soil = 2.6 W/m K (as per ashrae for saturated soil)
d = burial depth to centerline of pipe= 1.87 m
r0 = outer radius of pipe = 0.62 m
Rp = {ln(r0/r1)}}/ 2 pi Kp (negligible)
Ri = {ln(r2/r0)}}/2 pi Ki
Rp = thermal resistence of pipe (negligible)
Ri = thermal resistence of insulation
r1 = internal radius of pipe = 0.6 m
r2 = outer radius of insulation = 0.67 m
Kp = thermal conductivity of pipe (negligible)
Ki = thermal conductivity of insulation = = 0.026 W/m K (polyurethane foam)
Rt = total thermal resistence = Ri + Rs
q = (Ts-Tf)/Rt
q = total heat gain W/m
Ts = average annual soil Temp. = 30 deg. Celsius
Tf = fluid Temp. = 5 deg. Celsius
any help please





RE: Heat gain in buried chilled water pipes
Steady state means that the flow, water, soil and ambient temps are considered fixed for the basis of the calculation. c.f. transient calc, where something is changing.
RE: Heat gain in buried chilled water pipes
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RE: Heat gain in buried chilled water pipes