Heat transfer of an engine

In summary, the engine block is made of 1/2" thick cast iron and the internal temperature within the cooling passages is 260° F. The surface temperature on the outside of the block can be calculated using the thermal resistance of the material and the heat flow. The rate of new cold air arriving at the outside of the block is the most important factor in determining the temperature difference. Based on the given information, the outer surface of the engine block will be approximately 259° F.
  • #1

kosl

2
0
This is the scenario..

I have a engine and the block is made of cast iron which is 1/2" thick.

The internal temperature of the engine within the cooling passages is 260° F

Is there a way to calculate an approximate surface temperature on the outside of the engine block? If so, what would the temperature be?

Say that there was another cooling passage on the other side.. if the passage behind the 1/2" of iron was 260°, what would be the second cooling passages temperature?
 
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  • #2
So let me get this straight, as I'm not familiar with engine terms

you want the surface temperature of the 1/2 cast iron, and the air temperature a certain point above this surface?
 
  • #3
No, not really. The cast iron will act as a insulator, so the surfice teperature on the outside of the block will be less than on the inside of the block. I'm just wanting to know how much less.
 
  • #4
This is a thermal resistance question.
The temperature difference depends on the thermal resistance of the material and the heat flow. You can look up the temperature difference across a given thickness of cast iron for a given heat flow.

The complication comes when the temperature of the material on the other side isn't controlled. Suppose you want to know the temperature of air above the engine block.
Initially it is cold and you have a certain temperature difference across the cast iron, you can then work out the heat flow. But this heat flow will heat the air and so reduce the temperature difference, which will reduce the heat flow. Eventually the air is the same temperature as the inside of the engine then there is no temperature difference and so no heat flow.
Becuase of this, the most important factor is the rate of new cold air arriving at the outside of the engine.
 
  • #5
This is a combined heat transfer problem i.e. heat is conducted through the engine block and convected off the block by natural convection. It requires several simplifying assumptions such as:

* The engine block is modled as a horizontal plat with heated surface facing up
*The ambient room temperature is 80 degrees F
*You can neglect radiant heat transfer

q-conduction=q-convection

q-conduction= k*A/L(260-Ts)

q-convection= ho*A(Ts-80)

ho is the convective heat transfer coef (about 1.215 Btu/(hr*ft^2*F) for this problem) requires formulas for natural convection available in any Heat transfer text

k is thermal conductivity for cast iron

L is cast iron thickness in ft

Given the thin engine block wall and high conductivity of cast iron the outer surface of the engine block will be about 259 F
 

What is heat transfer and how does it affect engine performance?

Heat transfer is the movement of thermal energy from one object to another. In an engine, heat transfer plays a crucial role in determining its performance. The amount of heat transferred affects the temperature and pressure inside the engine, which in turn affects its efficiency and power output.

What are the different types of heat transfer in an engine?

There are three types of heat transfer that occur in an engine: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between two objects. Convection is the transfer of heat through the movement of fluids, such as air or coolant. Radiation is the transfer of heat through electromagnetic waves.

How is heat transfer controlled in an engine?

Heat transfer in an engine can be controlled through various methods, such as insulation, cooling systems, and design modifications. Insulation helps to reduce the amount of heat lost to the surroundings. Cooling systems, such as radiators and water pumps, help to remove excess heat from the engine. Design modifications, such as improved combustion chamber shape and materials, can also reduce heat transfer.

What is the role of lubrication in heat transfer of an engine?

Lubrication plays a crucial role in reducing the amount of heat transferred in an engine. It helps to reduce friction between moving parts, which in turn reduces heat generation. Proper lubrication also helps to dissipate heat away from critical engine components, keeping them at a safe operating temperature.

How does heat transfer affect the durability of an engine?

Excessive heat transfer can shorten the lifespan of an engine. High temperatures can cause metal components to expand and contract, leading to wear and tear. It can also cause thermal stress, which can result in engine failure. Therefore, managing heat transfer is essential for maintaining the durability of an engine.

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