Need help regarding heat transfer questions

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SUMMARY

This discussion focuses on solving heat transfer calculations involving a hot water cylinder and a plate heat exchanger. The first question involves determining the time required to heat 500 liters of water from 12°C to 60°C using a 30kW heat source. The second question seeks to calculate the mass flow rate for a plate heat exchanger rated at 400kW with an inlet temperature of 85°C and an outlet temperature of 40°C. The third question addresses the inlet temperature required for a water flow rate of 5kg/s from a 210kW source at 20°C.

PREREQUISITES
  • Understanding of heat transfer principles
  • Familiarity with the specific heat capacity of water
  • Knowledge of mass flow rate calculations
  • Basic thermodynamics concepts
NEXT STEPS
  • Calculate heating time using the formula Q = mcΔT for the hot water cylinder
  • Determine mass flow rate using the formula Q = ṁcΔT for the plate heat exchanger
  • Explore the relationship between flow rate and temperature in heat exchangers
  • Study the impact of varying inlet temperatures on heat exchanger efficiency
USEFUL FOR

Engineers, thermal system designers, and students studying heat transfer who need to solve practical problems related to heating systems and heat exchangers.

wattsie10
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Please can someone show me how to work out the following questions.

1) A hot water cylinder holds 500 litres. If the primary heat source is 30kW and the supply water inlet to the cylinder is 12°C, how long will it take to heat the whole tank to 60°C?

2) The primary side of a plate heat exchanger rated at 400kW has an inlet temperature of 85°C and the outlet temperature is 40°C. What is the mass flow rate?

3) To achieve a water flow rate of 5kg/s at 20°C from a 210kW source, what would be the temperature of the water as it enters the heat exchanger?

Many thanks
 
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Hi wattsie10! Welcome to PF! :wink:

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