# Applied Thermodynamics - Heat Exchanger problem

• asharp_pitt
In summary, the problem involves a heat exchanger operating at steady state with Refrigerant 134a as the working fluid. The refrigerant enters as a superheated vapor at 10 bars and 60C, is cooled and condensed to saturated liquid at 10 bars, and has a mass flow rate of 10 kg/min. Air also enters the heat exchanger at 37C with a mass flow rate of 80 kg/min. The goal is to determine the exit air temperature in degrees C. Two approaches can be used to solve this problem: analyzing the heat exchanger as an overall system or choosing a two-system setup with a continuity condition.
asharp_pitt

## Homework Statement

Refrigerant 134a enters a heat exchanger operating at steady state as a superheated vapor at 10 bars, 60C, where it is cooled and condensed to saturated liquid at 10 bars. The mass flow rate of the refrigerant is 10 kg/min. A separate stream of air enters the heat exchanger at 37C with a mass flow rate of 80 kg/min. Ignoring heat transfer from outside of the heat exchanger and neglecting kinetic and potential energy...

## Homework Equations

Determine the exit air temperature in degrees C.

## The Attempt at a Solution

I started with my conservation of mass and energy equation, and I have

for C.O.M, since its a steady state process, I have m(in) = m(out)

for C.O.E, I have Q-W=m(h(out)-h(in)) and..switched the change in enthalpy to cp(T2-T1) to find T2..

Is there something in particular you are stuck on with this problem? There are two ways to go about heat exchangers by system selection. Your first option is two analyze as an entire overall system noting that the entire system is adiabatic with respect to the environment (heat transfer out to the surroundings is usually negligible in comparison to the internal workings). The second option, that I prefer is to choose a two system setup where you note a continuity condition that the heat transfer out of one system is the heat transfer into the other system.

## 1. What is a heat exchanger?

A heat exchanger is a device that transfers heat from one fluid to another without the fluids coming into direct contact with each other. This is typically achieved through a series of tubes or plates that allow heat to be exchanged between the two fluids.

## 2. What is the purpose of a heat exchanger?

The main purpose of a heat exchanger is to efficiently transfer heat from one fluid to another. This can be used for various applications such as heating or cooling processes, energy recovery, and maintaining desired temperatures in industrial or residential settings.

## 3. How does a heat exchanger work?

A heat exchanger works by having two separate fluid streams flow through the device, with one stream being heated or cooled by the other. This transfer of heat occurs through the walls of the tubes or plates in the exchanger, which allows the fluids to maintain their own separate paths while still exchanging heat.

## 4. What are the different types of heat exchangers?

There are several types of heat exchangers, including shell and tube, plate and frame, and air-cooled. These differ in their design and the way in which heat is exchanged between the fluids. Some may be more suitable for certain applications or have higher efficiency than others.

## 5. How do you calculate the performance of a heat exchanger?

The performance of a heat exchanger can be calculated by determining the amount of heat transferred between the two fluids and the temperature difference between them. This can be calculated using equations such as the heat exchanger effectiveness or the log mean temperature difference method. Other factors such as flow rate, fluid properties, and design also play a role in determining the overall performance of a heat exchanger.

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