Transient heat transfer in heat exchangers

In summary, the conversation discusses a system with an engine generating 140 kW of thermal heat, which disturbs the thermal equilibrium of the engine. To cool the engine, a radiator is installed and water is cooled inside a heat exchanger with air. The system has a transient equation, but the speaker is having trouble solving it and asks for help with identifying the area of the heat exchanger. The initial conditions and known values are provided, but there are still two unknowns in the equation. The speaker is seeking guidance on how to design a radiator for this system and is asking for assistance.
  • #1
firavia
137
0
Considering an engine generating thermal heat at 140 kw and when the generation starts the thermal equilibrium of the engine will be distrubed , a radiator is installed to cool the engine this radiator cool the engine through flow of water and water is cooled inside a heat exchanger with air .
I set a transient equation to my system but I am still unable to solve it please check my equation if it is correct and if there is anything missing .

Qgen+mdot.cp water.(Tentring water - T exiting water)=[tex]\rho[/tex]C .V . dTengine/dt
P.S:ignoring radiation trasfer.
Qgen = 140 kw .
mdot water=0.37m3/s.
cpwater=4.1855 J/(g·K)
C cast iron=0.46
Rho=7870KG/m3.
v=>volume=0.01m3.
Initial conditions:
at t=0sec Tengine = 45 Deg Twater entring = 30 deg c
How can I design a radiator for such system , after solving the equation I still have 2 unknowns Thot air and T2 engine .
From the above how can I identify the area of my heat exchanger ?
 
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  • #2
Pleas I would like to know where I am wrong
 
  • #3
Nobody want to help me ?!
 

1. What is meant by transient heat transfer in heat exchangers?

Transient heat transfer in heat exchangers refers to the process of heat transfer that occurs over a period of time, rather than at a steady state. This means that the temperature difference between the hot and cold fluids in the heat exchanger is constantly changing, and the rate of heat transfer is not constant.

2. What factors affect transient heat transfer in heat exchangers?

There are several factors that can affect transient heat transfer in heat exchangers, including the flow rate and properties of the fluids, the geometry of the heat exchanger, the thermal conductivity of the materials used, and the initial temperature difference between the hot and cold fluids.

3. How is transient heat transfer different from steady state heat transfer?

Transient heat transfer is different from steady state heat transfer in that it occurs over a period of time, rather than at a constant rate. In steady state heat transfer, the temperature difference between the hot and cold fluids remains constant and the rate of heat transfer is also constant.

4. Why is it important to consider transient heat transfer in heat exchangers?

It is important to consider transient heat transfer in heat exchangers because many real-life applications involve processes that are not at steady state. Understanding and accurately predicting transient heat transfer can help improve the efficiency and performance of heat exchangers in these applications.

5. How is transient heat transfer calculated in heat exchangers?

Transient heat transfer in heat exchangers can be calculated using mathematical models and numerical methods, such as finite difference or finite element analysis. These models take into account the various factors that affect transient heat transfer and can provide valuable insights into the behavior of heat exchangers over time.

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