Different no. 0.332, 2m/s, 278K, Pr= 0.70, Vis 17.2x106, 1.16 kg/m³, 0.023 W/mK, 323 K, £0.40 per kWh The roof of a sauna loses heat by convection to a flow of air, and the Nusselt number of this flow has been determined to be Nuh = 0.332 (Reh) 0.5 Pr¹/3 The air flows at a velocity of 2 m/s and has a free stream temperature of 278 K. The properties of air are: Prandtl number Pr=0.70, viscosity u-17.2x10-6 Pa-s, density p = 1.16 kg/m³, and thermal conductivity k=0.023 W/mK. The sauna temperature is maintained constant at 323 K using an electric heater at a cost of £0.40 per kWh. The length of the roof in the parallel to the air flow is 2.5 m. a) The average heat transfer coefficient is b) The dimension of the roof perpendicular to the air flow is 6 m, and the roof can be assumed to be the same temperature as the sauna inside. The magnitude (don't include the sign) of the total heat loss from the roof is c) The cost per day of maintaining the temperature of the sauna is £ W/m²K. W.

Elements Of Electromagnetics
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answer choices are  0.34, 0.38, 0.42, 0.54, 0.85, 2.20, 2.58, 2.67, 3.11, 3.15, 1484, 1803, 2087, 2101, 2126

Different no. 0.332, 2m/s, 278K, Pr=0.70, Vis 17.2x106, 1.16 kg/m³, 0.023 W/mK, 323 K, £0.40
per kWh
The roof of a sauna loses heat by convection to a flow of air, and the Nusselt number of this
flow has been determined to be
0.5
Nuh 0.332 (Re) Pr¹/3
L
=
The air flows at a velocity of 2 m/s and has a free stream temperature of 278 K. The properties
of air are: Prandtl number Pr=0.70, viscosity u-17.2x10-6 Pa-s, density p = 1.16 kg/m³, and
thermal conductivity k=0.023 W/mK. The sauna temperature is maintained constant at 323 K
using an electric heater at a cost of £0.40 per kWh. The length of the roof in the parallel to the
air flow is 2.5 m.
a) The average heat transfer coefficient is
b) The dimension of the roof perpendicular to the air flow is 6 m, and the roof can be assumed
to be the same temperature as the sauna inside.
The magnitude (don't include the sign) of the total heat loss from the roof is
c) The cost per day of maintaining the temperature of the sauna is £_
W/m²K.
11
W.
Transcribed Image Text:Different no. 0.332, 2m/s, 278K, Pr=0.70, Vis 17.2x106, 1.16 kg/m³, 0.023 W/mK, 323 K, £0.40 per kWh The roof of a sauna loses heat by convection to a flow of air, and the Nusselt number of this flow has been determined to be 0.5 Nuh 0.332 (Re) Pr¹/3 L = The air flows at a velocity of 2 m/s and has a free stream temperature of 278 K. The properties of air are: Prandtl number Pr=0.70, viscosity u-17.2x10-6 Pa-s, density p = 1.16 kg/m³, and thermal conductivity k=0.023 W/mK. The sauna temperature is maintained constant at 323 K using an electric heater at a cost of £0.40 per kWh. The length of the roof in the parallel to the air flow is 2.5 m. a) The average heat transfer coefficient is b) The dimension of the roof perpendicular to the air flow is 6 m, and the roof can be assumed to be the same temperature as the sauna inside. The magnitude (don't include the sign) of the total heat loss from the roof is c) The cost per day of maintaining the temperature of the sauna is £_ W/m²K. 11 W.
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