How Does Effectiveness Influence Heat Exchanger Capacity Selection?

In summary: Cmin is the minimum heat capacity rate of both fluids (the smaller of the two)In summary, calculating the thermal efficiency of a heat exchanger is necessary in order to determine the required capacity for a given application. This can be done by calculating the effectiveness, which is the ratio of actual heat transfer to the maximum possible heat transfer. The maximum possible heat transfer can be found by multiplying the minimum heat capacity rate of both fluids by the difference in temperatures between the hot and cold fluids at the entrance. This information can be found in resources such as the air conditioning handbook or through online sources like Scribd and Air Resource LLC.
  • #1
cabellos2
16
0
heat exchanger efiiciency??

I have done some design work calculations for a double pipe heat exchanger. I have the inlet and outlet temperatures and mass flow rates etc. I have calculated Q the heat transfer rate.

However I am confused with the idea of the thermal efficiency of the heat exchanger. In order to select the required capacity of heat exchanger i need to factor in an efficiency somehow.

Do I work out the effectiveness and then when i get this value I choose my capacity of heat exchanger (e.g if the effectiveness is 0.5 then I double the initial Q value to select the heat exchanger capacity)??
 
Engineering news on Phys.org
  • #2


hallo...

for your problem, may you can get heat exchangher information on air conditioning hand book

you can download in at scribd.com

irian
blog : http://irianpoo.blogspot.com
 
  • #3


Most domestic hvac systems have a rated capacity before they are installed. The technician then comes along, installs the system, charges it with refrigerant, runs a test & then leaves. Whether the system ever reaches the rated capacity would have to tested or simulated.

The operating capacity of each exchanger in the system will certainly be affected by the prevailing local conditions eg. room volume/temp, or outside temperature.

Webb & Kim, Principles of Enhanced Heat Transfer

http://www.mne.psu.edu/webb/"

http://www.airresourcellc.com"
 
Last edited by a moderator:
  • #4


You can calculate the effectiveness. e = q/qmax

q max = Cmin (Thi - Tci)

Thi is temperature of the hot fluid at the entrance
Tci is " " of cold " "
 

1. What is a heat exchanger and how does it work?

A heat exchanger is a device that transfers heat from one fluid to another without the two fluids mixing. This is achieved through a series of tubes or plates that allow one fluid to flow through while the other fluid flows around it. The heat is transferred through the walls of the tubes or plates, resulting in a temperature change in both fluids.

2. How is the efficiency of a heat exchanger measured?

The efficiency of a heat exchanger is typically measured by the effectiveness or the heat transfer coefficient. Effectiveness is the ratio of the actual heat transfer to the maximum possible heat transfer, while the heat transfer coefficient is the rate at which heat is transferred through the exchanger per unit of surface area.

3. What factors affect the efficiency of a heat exchanger?

The efficiency of a heat exchanger is affected by several factors, including the flow rate of the fluids, the temperature difference between the two fluids, the type and design of the heat exchanger, and the fouling or build-up of deposits on the heat transfer surfaces.

4. How can the efficiency of a heat exchanger be improved?

There are several ways to improve the efficiency of a heat exchanger. These include increasing the surface area for heat transfer, improving the flow patterns of the fluids, using more efficient materials for construction, and implementing regular maintenance and cleaning to prevent fouling.

5. What are some common types of heat exchangers?

Some common types of heat exchangers include shell and tube heat exchangers, plate heat exchangers, and double-pipe heat exchangers. Each type has its own advantages and is used in different industries and applications, depending on the specific heat transfer requirements.

Similar threads

Exit flow rate in a Plate Heat Exchanger
    • Mechanical Engineering
Replies
4
Views
1K
Undefined log-mean temperature in heat exchanger design
    • Mechanical Engineering
Replies
3
Views
1K
Plate heat exchanger NTU method effectiveness
    • Mechanical Engineering
Replies
1
Views
2K
Exam help regarding heat exchanger, forced convection questions
    • Mechanical Engineering
Replies
7
Views
2K
How Long Should My Double Pipe Heat Exchanger Be for a 22kW Capacity?
    • Mechanical Engineering
Replies
2
Views
1K
Fin/Fan heat exchanger mass and energy balance
    • Mechanical Engineering
Replies
3
Views
2K
Seawater sample temperature control – heat exchanger design
    • Mechanical Engineering
Replies
12
Views
2K
How can I calculate the heat transfer in an air to air heat exchanger?
    • Mechanical Engineering
Replies
22
Views
2K
Spec'ing the power of heater for an atypical heat exchanger problem
    • Engineering and Comp Sci Homework Help
Replies
22
Views
1K
Calculation of water flow rate in heat exchanger
    • Mechanical Engineering
Replies
6
Views
11K

Hot Threads

Recent Insights

Back
Top