Thermodynamics homework help, water cooled air cooler

In summary, the conversation revolves around finding the air density or velocity at entry for a heat exchanger problem. The person is seeking guidance to help them calculate the heat load and is unsure where to find the necessary information. They ask for advice on applying the open system version of the first law of thermodynamics to the air side of the heat exchanger and are looking for a suitable statement of this law to use for their problem. Some potential resources for this information are suggested, including online textbooks and a website with a relevant chapter.
  • #1
elecone
4
2
Homework Statement
A water cooled air cooler (WCAC) has the following conditions:

Air cooler:
mass flow rate: 10kg mins^-1
entry air temp: 300 degrees c
entry air pressure: 2 bar
entry pipe diameter: 0.1m
velocity of air on exit: 25 ms^-1

Water cooler:
mass flow rate: 10 kg min^-1
water temp increase by 50 degrees c

the heat transfer from air to water has an efficiency of 100%

Air Cp = 1.004 KJ Kg^-1K^-1
Air Cv = 0.717 KJ Kg^-1K^-1
Water specific heat = 4.187 KJ Kg^-1K^-1

What is the temperature of the air as it leaves the WCAC
Relevant Equations
pV=mRT
R=cp/cv
ṁ=pAC
I'm not looking for someone to tell me the answer, just help steer me in the right direction.

I feel like I need to find the air density or air velocity at entry to proceed, but I'm unsure

any help and guidance is greatly apricated!
 
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  • #2
no takers?
 
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From the water data, what is the heat load (the rate of transfer of heat to the water)? If you apply the open system (control volume) version of the first law of thermodynamics to the air side of the heat exchanger, what do you get for the relationship between the mass flow rate of air, the enthalpy change per unit mass of the air, and the heat load?
 
  • #4
Chestermiller said:
If you apply the open system (control volume) version of the first law of thermodynamics to the air side of the heat exchanger, what do you get for the relationship between the mass flow rate of air, the enthalpy change per unit mass of the air, and the heat load?
Excuse my ignorance but where I can find a statement of the open system version of the 1st law that is suitable for application to this problem. I tried wikipedia but without success , the section for open systems there seems not well written.
 
  • #5
Delta2 said:
Excuse my ignorance but where I can find a statement of the open system version of the 1st law that is suitable for application to this problem. I tried wikipedia but without success , the section for open systems there seems not well written.
Fundamentals of Engineering Thermodynamics, Moran et al, available on line

Introduction to Chemical Engineering Thermodynamics, Smith and van Ness

Chemical Engineers' Handbook, Perry et al

http://www.rshanthini.com/yahoo_site_admin/assets/docs/ThermoChap09.20063703.pdf
 
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FAQ: Thermodynamics homework help, water cooled air cooler

What is thermodynamics?

Thermodynamics is the branch of science that deals with the relationship between heat, energy, and work. It studies how energy is transferred and transformed between different forms, such as heat and mechanical work.

What is a water cooled air cooler?

A water cooled air cooler is a type of cooling system that uses water as a medium to remove heat from the air. It works by circulating water through a series of pipes or tubes, which are then cooled by a fan or other means, and then the cooled water is used to cool the air passing through the system.

How does a water cooled air cooler work?

A water cooled air cooler works by using a heat exchanger to transfer heat from the air to the water. The water is then circulated to a cooling tower, where it is cooled by evaporation, and then returned to the heat exchanger to repeat the process. This cycle continues until the desired temperature is reached.

What are the advantages of using a water cooled air cooler?

There are several advantages to using a water cooled air cooler. Firstly, it is more energy efficient compared to other cooling systems, as water has a higher heat capacity and can absorb more heat. It also allows for more precise temperature control and can be used in a wide range of applications.

Are there any disadvantages to using a water cooled air cooler?

One of the main disadvantages of a water cooled air cooler is the need for a constant water supply and a cooling tower, which can be expensive to install and maintain. It also requires regular maintenance to prevent scaling and other issues. Additionally, the use of water can pose environmental concerns if not properly managed.

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