Problemas Intercambiadores de calor

If the outlet temperature of the oil is 60C, determine the total heat transfer rate.

• 8000 W

• 7500 W

• 7600 W

• 7400 W

Determine the outlet temperature of the water

• 45.1

• 46.1

• 48.1

• 50.1

Determine the length of the heat exchanger

• 45.3 m

• 46.3 m

• 48.3 m

• 40.3 m

What are the heat transfer mechanisms involved during heat transfer from the hot to the cold fluid?

• Convection and Conduction

• Radiation and Convection

• Conduction , Radiation and Convection

• Convection

Is the approximation hi = ho = h for the convection heat transfer coefficient in a heat exchanger a reasonable one when the thickness of the tube wall is negligible?

• True

• False

A double-pipe counter-flow heat exchanger is to cool ethylene glycol (Cp = 2560 J/kg · °C) flowing at a rate of 3.5 kg/s from 80°C to 40°C by water (Cp = 4180 J/kg · °C) that enters at 20°C and leaves at 55°C. The overall heat transfer coefficient based on the inner surface area of the tube is 250 W/m2 · °C. Determine the rate of heat transfer.

• 400 kW

• 358.4 kW

• 350.3 kW

• 360.5 kW

A double-pipe counter-flow heat exchanger is to cool ethylene glycol (Cp = 2560 J/kg · °C) flowing at a rate of 3.5 kg/s from 80°C to 40°C by water (Cp = 4180 J/kg · °C) that enters at 20°C and leaves at 55°C. The overall heat transfer coefficient based on the inner surface area of the tube is 250 W/m2 · °C. Determine the mass flow rate of water.

• 3.1 kg/s

• 2 kg/s

• 2.45 kg/s

• 2.7 kg/s

A double-pipe counter-flow heat exchanger is to cool ethylene glycol (Cp = 2560 J/kg · °C) flowing at a rate of 3.5 kg/s from 80°C to 40°C by water (Cp = 4180 J/kg · °C) that enters at 20°C and leaves at 55°C. The overall heat transfer coefficient based on the inner surface area of the tube is 250 W/m2 · °C. Determine the heat transfer surface area using LMTD method.

• 60 m²

• 68 m²

• 67 m²

• 64 m²

A heat exchanger is used to condense steam coming off the turbine of a steam power plant by cold water from a nearby lake. The cold water (cp = 4.18 kJ/kg⋅ºC) enters the condenser at 16ºC at a rate of 20 kg/s and leaves at 25ºC while the steam condenses at 45ºC (h_fg=2395 kJ/kg). The condenser is not insulated and it is estimated that heat at a rate of 8 kW is lost from the condenser to the surrounding air. Determine the mass flow rate at which the steam condenses.

• 0.318 kg/s

• 0.282 kg/s

• 0.290 kg/s

• 0.305 kg/s

A heat exchanger is used to heat cold water(cp=4.18 kJ/kgC) entering at 8°C at a rate of 1.2 kg/s by hot air (cp= 1kJ/kgC) entering at 90°C at rate of 2.5 kg/s. The highest rate of heat transfer in the heat exchanger is:

• 114 kW

• 411 kW

• 205 kW

• 300 kW