[sakthi]

I am doing the design of heat exchangers......

I need a help for thermal design.... can you help me. Here I have noticed my procedures and problems...

1.Q=m cp dT
2.m1 cp1 dT =m2 cp2 dT
3.Finding U(h) AND ^T
4.A= Q/ U*^T
For finding no.of tubes
5. Flow rate = AREA* VELOCITY
by assumption, average velocity =0.9 m/sec....... will find area.
6.for 5/8 OD i will get no.of tubes n*pi*d2/4 = area
For finding length,
7. surface area = 2*pi*r*h* n
will find h value- length of the tube...
for reducing length i will use correction factor in area formula.
THEN will continue MECHANICAL DESIGN.
HERE I have doubt in
1. HOW TO ASSUME VELOCITY FOR PROPER HEAT TRANSFER.
2.PRESSURE DROP IN CALCULATION AND EFFECTIVE LENGTH OF HEAT EXCHANGER...
3.ANY OTHER METHOD FOR THERMAL DESIGN...
4.FINDING SHELL SIDE HEAT TRANSFER COEFFICIENT...

[bighead]

if u google under BOOKS, look for this "fundamentals of heat exchanger design" by RK Shah. May not be able to see the whole book, but some parts should be viewable.

[Sanjv9473]

A heat exchanger involves two flowing fluids separated by a solid wall. Heat is transferred from the hot fluid to the wall by convection, through the wall by conduction and from the wall to the cold fluid by convection.

How is heat exchanger design calculated?
Preliminary heat exchanger design to estimate the required heat exchanger surface area can be done using the basic heat exchanger equation, Q = U A ΔTlm, if values are known or can be estimated for Q, U and ΔTlm. Heat exchanger theory tells us that ΔTlm is the right average temperature difference to use

[Guvennergiz]

No need to type more or less comment than a very very usefull book: https://www.amazon.com/Heat-Exchange.../dp/1439849900

That is you all need.

[mcanoenen]

Actually I was interested in the subject in my graduation thesis. Here how I go to design a heat exchanger:

I hope the following method give you some lead to achieve a solution.

Known Entities (let me define an example case):

- Heat exchanger type: Let it be shell and tube heat exchanger.
- Desired inlet Tin1 and outlet Tout1 temperatures of the fluid, doesnt matter if the tube-side or in the shell-side. and known other temperature Tin2.
- mass flow rates of shell-side and tube-side

Calculator:

1) Calculate the Q with Q=m*cp*|(T_in1-T_out1)| and find the unknown outlet temperature T_out2,
1) Initially guess the number of tubes say n=10
2) Find the heat transfer coeffficent for tube and shell sides (Sadık Kakac has a book you can consult to)
3) Calculate " normal to the boundaries" heat transfer rate. Qr=U*A*DTLM -you will get an equation depending on the number of tubes- (DTLM: Logaritmic Mean Temperature Difference)
4) Calculate the required number of tubes, n=Q/Qr . Say you found like n=23. Which shows n=10 is wrong as an initial assumption
5) Guess the number of tubes say n=23. With an assumption n=23, solve the above routine again. Iterate like this untill the calculated number of tubes is equals to the guessed number of tube number.


regards,

mcanoenen

[Lordfintube]

Does anyone how to caculate the finned tube weight and finned tube heat transfer surface? Is there any formula?

[Lordfintube]

The heat exchange area of the finned tube includes the effective surface area of the base tube and the entire outer surface area of the exposed portion of the fins.
Calculation method of heat exchange area of finned tubes (taking steel and aluminum finned tubes as an example)
For example: a finned tube is 1860mm long, and both ends are 30mm empty without fins. The diameter of the finned tube is 25mm, the bottom diameter thickness is 0.5mm, the tube thickness is 2mm, and the fin spacing is 2. 8mm, sheet thickness 0.35mm, fin outer diameter 57, effective sheet height 15.5mm, what is the heat exchange area of a finned tube?
Answer: The calculation of the heat exchange area is generally based on the cumulative addition of all the parts exposed to the air, which can be divided into three parts.
1, the surface area of the base pipe part (the thickness of the sheet needs to be deducted)
2, the top of the fin (the surface area after the effective number of fins is accumulated)
3. The surface area of the front and back sides of the fin. The sum of these three numbers is the heat exchange area of the finned tube.