Design Process of a heat exchanger(evaporator) and fan

In summary, designing an evaporator and sizing the fan for forced convection involves considering factors such as the power to be dissipated, ambient air temperature, and air density. Knowledge of thermodynamics, heat transfer, and fluid dynamics is important for this design. It is recommended to make initial estimates for the number of fins and fan size, and then iterate to find the optimal solution. Optimization studies can also help in minimizing the number of fins or volume of the heat exchanger. Various resources on thermodynamics, heat transfer, and fluid dynamics can provide guidance for this design project. Calculations involved may include determining the surface area of fins and flow area of the exchanger.
  • #1
droc22
10
0
Hello,

I need help with my fourth-year design project. The part that I need particular help with is how to design an evaporator and how to size the fan that will create the forced convection over the fins.

What are the main things to consider in terms of design steps?

What are some good resources that will point me in the right direction?

What calculations are involved?

Any help you can provide would be great.

Thanks,
 
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  • #2
Well, basically you will have to take into account the following things-

- The maximum amount of power (W) you need to dissipate through the heat exchanger
- The worst-case (highest) ambient air temperature your heat exchanger will be exposed to
- Air density (sea level, 30,000ft asl, wherever)

Subjects most pertinent to this design would be thermodynamics, heat transfer, and fluid dynamics. With a basic grasp of these subjects, you should have everything you need.

You will probably need to start with a guess at how many fins your heat exchanger will likely have (and how the fluid might travel through the fins), and their approximate surface area, and the flow area of the exchanger (rough estimates are fine, since you will probably end up iterating towards a final solution). Alternatively you could guess at a size fan you want based on the ambient air temperature and the projected air temperature using the power being dissipated. Then, you could work out how many fins you would need and how big they would need to be.

With the above quantities, you can calculate how much heat you can dissipate from the exchanger based on an amount of air flow, and iterate to find a properly sized fan. It is also possible to do an optimization study to minimize the number fins or the volume of the heat exchanger by looking at relationships of the design parameters with respect to each other. Things like how changing the number of fins changes their required surface area,of the size of the fan versus the amount of air it can push.
 
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1. What is the purpose of a heat exchanger (evaporator) and fan in a system?

The purpose of a heat exchanger (evaporator) and fan is to transfer thermal energy from a hot fluid to a cooler fluid, resulting in temperature change or phase change in the cooler fluid. This process is important in various applications such as refrigeration, air conditioning, and chemical processes.

2. How does the design process of a heat exchanger (evaporator) and fan work?

The design process of a heat exchanger (evaporator) and fan involves several steps, including determining the desired heat transfer rate, calculating the heat duty, selecting the appropriate heat transfer surface area and type of heat exchanger, and sizing the fan to provide sufficient air flow for heat exchange.

3. What factors should be considered when designing a heat exchanger (evaporator) and fan?

Some important factors to consider when designing a heat exchanger (evaporator) and fan include the desired heat transfer rate, fluid properties and flow rates, operating temperatures and pressures, materials of construction, and space and budget constraints. It is also important to consider any potential fouling or corrosion issues that may affect the design.

4. How can the efficiency of a heat exchanger (evaporator) and fan be improved?

The efficiency of a heat exchanger (evaporator) and fan can be improved by optimizing the design to minimize thermal resistance and pressure drop, selecting materials with high heat transfer coefficients, and using techniques such as fins or turbulators to enhance heat transfer. Proper maintenance and cleaning can also help improve efficiency and prolong the lifespan of the equipment.

5. What are some common types of heat exchangers (evaporators) and fans used in industrial applications?

Some common types of heat exchangers (evaporators) include shell and tube, plate and frame, and spiral heat exchangers. Fans used for heat exchange can vary in type, such as centrifugal, axial, or mixed flow fans. The selection of the appropriate type and size of heat exchanger and fan will depend on the specific application and design requirements.

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