A cylindrical hot water tank has thermal insulation between an inner and an outer wall of...
A cylindrical hot water tank has thermal insulation between an inner and an outer wall of thin metal sheets, both on the sidewalls and the end walls. The inner diameter and height is 0.95 m and 2.6 m respectively. The insulation thickness is 64 mm and its thermal conductivity is λ = 0.051 [W/mK]. The inner wall consists of 3.0 mm stainless steel with λ = 25 [W/mK], and the outer wall consists of 1.3 mm steel sheet with λ = 45 [W/mK]. The water tank is placed in a room with air temperature 15 ^0C, and the coefficient of heat transfer on the air side is α = 15 [W/m^2 K].
a) Assuming that the hot water temperature is 82 degress Celsius, How large is the heat loss and the energy cost per day (24 hours)? The energy price can be set to 0.095 [EURO/kWh].
b) Make an assessment of the error of the heat flow by neglecting the heat resistance in the inner and outer metal walls.
Homework Answers
The system can be modeled as the Current-Voltage system
RH- resistance of individual part.
R- radius
Resistance in cylindrical solid= ln(R2/R1)/(2πLk)
K is thermal conductivity (W/mK)
Resistance of convection= 1/(coefficient of convection*area)
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