List of top Heat Transfer Questions asked in GATE Chemical Engineering

A solid slab of thickness \( H1 \) is initially at a uniform temperature \( T0 \). At time \( t = 0 \), the temperature of the top surface at \( y = H1 \) is increased to \( T1 \), while the bottom surface at \( y = 0 \) is maintained at \( T0 \) for \( t \geq 0 \). Assume heat transfer occurs only in the \( y \)-direction, and all thermal properties of the slab are constant. The time required for the temperature at \( y = \frac{H1}{2} \) to reach 99% of its final steady value is \( T1 \). If the thickness of the slab is doubled to \( H2 = 2H1 \), and the time required for the temperature at \( y = \frac{H2}{2} \) to reach 99% of its final steady value is \( T2 \), then \( \frac{T2}{T1} \) is .

The temperatures of two large parallel plates of equal emissivity are 900 K and 300 K. A reflection radiation shield of low emissivity and negligible conductive resistance is placed parallelly between them. The steady-state temperature of the shield, in K, is

The opposite faces of a metal slab of thickness 5 cm and thermal conductivity 400 W m\(^{-1}\) °C\(^{-1}\) are maintained at 500 °C and 200 °C. The area of each face is 0.02 m\(^2\). Assume that the heat transfer is steady and occurs only in the direction perpendicular to the faces. The magnitude of the heat transfer rate, in kW, rounded off to the nearest integer, is ____.

Hot oil at \( 110^\circ \)C heats water from \( 30^\circ \)C to \( 70^\circ \)C in a counter-current double-pipe heat exchanger. The flow rates of water and oil are \( 50 \) kgmin\(^{-1}\) and \( 100 \) kgmin\(^{-1}\), respectively, and their specific heat capacities are \( 4.2 \) kJ kg\(^{-1}\)°C\(^{-1}\) and \( 2.0 \) kJ kg\(^{-1}\)°C\(^{-1}\), respectively. Assume the heat exchanger is at steady state. If the overall heat transfer coefficient is \( 200 \) W m\(^{-2}\)°C\(^{-1}\), the heat transfer area \( A \) in m\(^{2}\) is:

If the Prandtl number Pr = 0.01, which of the following statements is/are correct?