4. A thin-walled tube of 20-mm diameter passes hot fluid at a mean temperature of 45 °C in anexperimental flow loop. The tube is mounted horizontally in quiescent air at a temperature of 15 °C.To satisfy the stringent temperature control requirements of the experiment, it was decided to windthin electrical heating tape on the outer surface of the tube to prevent heat loss from the hot fluid tothe ambient air. a. Neglecting radiation heat loss, calculate the heat flux qe that must be supplied by the electricaltape to ensure a uniform fluid temperature. b. Assuming the emissivity of the tape is 0.95 and the surroundings are also at 15 °C, calculate therequired heat flux.

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