Heat Transfer Mock Test 10

1. Which one is having the lowest value of specific heat?

2. In a surface condenser, the water flowing through a series of tubes at the rate of 200 kg/hr is heated from 15 degree Celsius to 75 degree Celsius. The steam condenses on the outside surface of tubes at atmospheric pressure and the overall heat transfer coefficient is estimated at 860 k J/m² hr degree. Find the effectiveness of the heat exchanger. At the condensing pressure, stream has a saturation temperature 0f 100 degree Celsius and the latent heat of vaporization is 2160 k J/kg. Further, the steam is initially just saturated and the condensate leaves the exchanger without sub-cooling i.e. only latent heat of condensing steam is transferred to the water. Take specific heat of water as 4 k J/kg K

3. What is the value of overall heat transfer coefficient ammonia condensers?

4. What is the value of fouling factor for engine exhaust?

5. What is the value of overall heat transfer coefficient for steam condensers?

6. A heat exchanger to preheat oil for a furnace was designed without considering the possibility of scale formation, and the overall heat transfer coefficient based on the fuel oil side was 3200 k J/m² hr degree. What would be the corrected coefficient of heat transfer if a fouling factor of 0.00025 m² hr degree/k J for the fuel oil is taken into account?

7. The lubricating oil for a large industrial gas turbine engine is cooled in a counter flow, concentric tube heat exchanger. The cooling water flows through the inner tube ( diameter = 25 mm) with inlet temperature 25 degree celsius and mass flow rate 0.2 kg/s. The oil flows through the annulus (diameter = 50 mm) with mass flow rate 0.125 kg/s and its temperature at entry and exit are 90 degree Celsius and 60 degree Celsius. Find outlet temperature of cooling water

8. Boundary layer thickness is given by

9. Local skin friction coefficient is given by

10. What is the thermal conductivity of cotton in W/m K?