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vishnu123
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I am trying to model an evaporator which evaporates water to steam in Matlab/simulink. Are there any governing equations i need to know and follow when modelling the evaporator mathematically? Please let me know.
Yes there are, of course.vishnu123 said:Are there any governing equations i need to know
What about a textbook, e.g. Luyben: Process Modeling, Simulation and Control for Chemical Engineersvishnu123 said:yes i tried but i need equations with respect to time and in a simple way.
(your post was hard to understand until I typeset the balances)vishnu123 said:here are the equations please check and do the necessary corrections.
Working fluid energy balance:
$$M_f\,{dh_f\over dt} = m_f\left ( h_{f,in}-h_{f,out}\right )+A_f \,U\,\left (T_w-T_{f,in}\right )$$Wall energy balance:
$$M_w-C_{p,w}\,{dT_w\over dt} = -A_f\,U\,(T_w-T_{f,in})-A_g\,U\,(T_w-T_{g,in})$$
Exhaust gas energy balance:
$$M_g-C_{p,\;g,{in}}{dT_g\over dt} = m_g(C_{p,\;g,{in}}\,T_{g, in} - C_{p,\;g,out}\,T_{g,out})+A_g\,U\,(T_w-T_{g,in})$$
Where ...
Sorry for misinterpreting your minus sign . If you use the right-mouse button while hovering above a ##\LaTeX## typeset equation, you can see the input to render equations in PF.vishnu123 said:In the equations it is not substract its a product
My point is that it is much easier to develop a working simple model first and then evolve it into something more detailed. You are basically setting up and solving an N equations times N variables calculation. If N is twice as big, it is four tiems more difficult to get it to work and check that is is correct.vishnu123 said:I am looking for a detailed dynamic model of the evaporator if the unknowns are too many i can go with the basic model.
Don't know Nag and Kurmi, but I suspect a lot of detail. Much better if you can find something more introductory such as Luyben. I have 2nd ed (1989 -- so don't buy but borrow) and ch 3.7 'Single component vaporizer' taylormade for your exercise !vishnu123 said:Refrigeration and air condition by P.K Nag, R.S Kurmi. If you know any better books
No. But the other way around: yes. If there is a change in phase, there is a change in enthalpy. A change, a jump, a discontinuity, whatever you want to call it. The enthalpy changes by ##h_{fg}## when the phase changes from liquid to gas at the boiling temperature.vishnu123 said:To my knowledge if there is a change in enthalpy that means there is a phase change. Is it correct?
The equation is suitable for an immersion heater with heat loss from the cup to the environment .BvU said:Again, I wonder what you are modelling
BvU said:The equation is suitable for an immersion heater with heat loss from the cup to the environment
Mathematical modeling of an evaporator for evaporating water is the process of creating a mathematical representation of the physical system of an evaporator used to remove water from a liquid mixture. This model helps to predict the behavior and performance of the evaporator under different conditions.
Mathematical modeling is important for evaporators because it allows engineers and scientists to analyze and optimize the design and operation of the evaporator. This can lead to improved efficiency, reduced energy consumption, and cost savings.
The factors considered in mathematical modeling of an evaporator include the physical properties of the liquid mixture, heat transfer coefficients, mass transfer coefficients, and the design and operating conditions of the evaporator such as temperature, pressure, and flow rate.
The accuracy of mathematical models of evaporators depends on the complexity of the model and the availability of accurate data for the system. Generally, the more detailed and accurate the model is, the more accurate the predictions will be. However, there may still be some discrepancies between the model and the actual system due to uncertainties and variations in real-world conditions.
Yes, mathematical models can be used to optimize evaporator performance by simulating different operating conditions and designs to determine the most efficient and cost-effective configuration. This can help to reduce energy consumption, improve product quality, and increase overall efficiency of the evaporator.