How do you calculate LMTD correction factor?
How do you calculate LMTD correction factor?
Hence a correction factor ‘F’ must be introduced in the general heat equation and the equation is modified as Q = UA (F) LMTD. This correction factor ‘F’ depends on the number of shells of the heat exchanger and on the terminal temperatures of the heat exchanger.
Why we use LMTD correction factor?
Why do we use LMTD Correction factor? Explanation: In a shell and tube heat exchanger we observe both counter current and concurrent flow at different regions of the shell. This phenomenon makes the use of complete countercurrent LMTD unsuitable for calculations.
What happens when LMTD is zero?
Zero LMTD means no further heat transfer is possible and if heat transfer is to be done than infinite area is required, which is not possible.
What is correction factor in shell and tube heat exchanger?
The correction factor is a measure of the heat exchanger’s departure from the ideal behavior of a counter flow heat exchanger having the same terminal temperatures. The correction factor depends on the efficiency of the temperature and the ratio of heat capacity for a particular flow arrangement.
What is the use of baffles?
Baffles serve two functions: Most importantly, they support the tubes in the proper position during assembly and operation and prevent vibration of the tubes caused by flow-induced eddies, and secondly, they guide the shell-side flow back and forth across the tube field, increasing the velocity and the heat transfer …
What is the limitations of LMTD method?
Assumptions and limitations However, if the specific heat changes, the LMTD approach will no longer be accurate. A particular case for the LMTD are condensers and reboilers, where the latent heat associated to phase change is a special case of the hypothesis.
What is fouling factor?
The fouling factor represents the theoretical resistance to heat flow due to a build-up of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger, but they are often overstated by the end user in an attempt to minimise the frequency of cleaning.
What is LMTD and LMTD correction factor can LMTD be zero What happen if that condition occurs?
The LMTD is a logarithmic average of the temperature difference between the hot and cold feeds at each end of the double pipe exchanger. For a given heat exchanger with constant area and heat transfer coefficient, the larger the LMTD, the more heat is transferred.
When can LMTD not be used?
A particular case where the LMTD is not applicable is condensers and reboilers, where the latent heat associated to phase change makes the hypothesis invalid. It has also been assumed that the heat-transfer coefficient (U) is constant and not a function of temperature.
What do you mean by correction factor?
A correction factor is a factor multiplied with the result of an equation to correct for a known amount of systemic error.
What is the purpose of the LMTD correction tool?
It is a computer tool for determining the LMTD correction factors for complex heat exchanger flow arrangements. The charted correction factors for various flow arrangements were curvefitted using the MS Excel Solver tool.
What is the minimum LMTD correction factor for heat exchanger design?
Perrys Chemical Engineers’ Handbook states LMTD correction factors lower than 0.8 indicate inefficient heat exchanger design, while the Heat Exchanger Design Handbook advises that the minimum value should be 0.75.
What does LMTD stand for?
Calculates Logarithmic Mean Temperature Difference (LMTD) Correction factor for different configuration of exchangers.
What is LMTD heat transfer method?
With the LMTD method, the task is toselecta heat exchanger that will meet the prescribed heat transfer requirements. 16‐04‐2014 2 Tman appropriate mean (average) temperature difference between the two fluids
