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4. A flat horizontal plate made of carbon steel with an emissivity of 0.39 measures 2.5 m by 2.5 m square and is initially at 95 °C. The top of

the plate is exposed to solar radiation, absorbing an incident heat flux of 1200 W/m?. The top of the plate is also exposed to air with surroundings at 25 °C, and a free convection heat transfer coefficient of 12.4 W/m?-K. The plate is thin, so the side surfaces can be ignored, but the bottom of the plate (which is also initially at 95 °C) is exposed to a stream of cold water at 15 °C with a forced convection heat transfer coefficient of 41.2 W/m?-K. Include heat transfer by radiation leaving the top surface of the plate in your calculations, but radiation through the water may be ignored. A. Will the plate HEAT UP. COOL DOWN or STAY AT 95 °C? B. What temperature should the water be to maintain a steady state plate temperature of 95 °C?

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