Heat cross exchanger

AI Thread Summary
A user is troubleshooting a cross flow heat exchanger where hot air enters at 150 degrees Celsius and water flows at 0.5 kg/s with an inlet temperature of 12 degrees Celsius, aiming for an outlet of 85 degrees. They seek guidance on using an online steam calculator, specifically which prompts to select for accurate calculations. Concerns arise about the number of coil rows needed for effective heat transfer and whether the cold water is fed from the correct side of the coil. The discussion highlights the importance of multiple coil layers to enhance heat exchange efficiency and prevent heat loss in a single-pass system. Overall, understanding the setup and proper inputs for calculations is crucial for optimizing the heat exchanger's performance.
cowboyMorty
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TL;DR Summary
How do I break down this question for inputs for viscosity etc
I have a problem with a cross flow heat exchanger. Hot air enters at 150 degrees at a flow rate of 4.0m^3 s^-1 and a flow speed of 12m s^-1

Water has a flow rate of 0.5kg s^-1 in the tube which has a 50mm diameter

Inlet of the water is 12 degrees and decided outlet is 85

I am confident in my ability to answer the question but having one problem, I have to use an online steam calculator and need help which what prompts to use

My calculator prompts are

Pressure / temperature

Pressure / specific enthalphy

Pressure / specific entropy

Pressure / specific volume

Temperature / specific entropy

Temperature/ quality

Is there something I'm missing, I feel that temperature and specific entropy is the correct one but where do I get my entropy figures?

Any help would be appreciated
 
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Welcome to PF, Morty. Is this question for schoolwork?
 
Welcome!
Why do we have water, steam and hot air inside the same heat exchanger?
 
cowboyMorty said:
TL;DR Summary: How do I break down this question for inputs for viscosity etc

I have a problem with a cross flow heat exchanger. Hot air enters at 150 degrees at a flow rate of 4.0m^3 s^-1 and a flow speed of 12m s^-1

Water has a flow rate of 0.5kg s^-1 in the tube which has a 50mm diameter

Inlet of the water is 12 degrees and decided outlet is 85

I am confident in my ability to answer the question but having one problem, I have to use an online steam calculator and need help which what prompts to use

My calculator prompts are

Pressure / temperature

Pressure / specific enthalphy

Pressure / specific entropy

Pressure / specific volume

Temperature / specific entropy

Temperature/ quality

Is there something I'm missing, I feel that temperature and specific entropy is the correct one but where do I get my entropy figures?

Any help would be appreciated
You will run into more problems, like how many rows of coils the air passes through. Are you feeding the cold water into the back of the coil, the side the air is leaving? One row will probably not extract enough heat from the air to raise the temperature of the water. Most evaporation coils have multiple layers for that reason. It also saves space.

Things like, "Are you recirculating the air?" Mater as well, if you do not want to waste the heat in the air of a single-pass system.

With a multilayer coil, the water leaving the system is polished to perfection on the face of the coil receiving the incoming hot air. Because the water has been pre-warmed by the air that passes through the first layer or layers of the coil.
 
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