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  1. J

    Convection heat exchanger

    Thank you for that! I understand it much better now!!! In my thermo course, I think we just used steam tables for pure substances and the ideal gas equation for air. So I'd never dealt with a situation where the temperature was a function of time. I'm doing a second course later this year which...
  2. J

    Convection heat exchanger

    Ah! Sorry Here goes, $$\dot{Q} + \dot{m}(h_1 - h_2) = \dot{m}(u_2 - u_1)$$ Heat is from convection so, $$hA_c(T_h-T_o) = \dot{m}(c_p + c_v)(T_o-T_i)$$ Is that correct? Why would ##T_i## be a constant but not ##T_o##?
  3. J

    Convection heat exchanger

    $$\dot{Q} - \dot{W} = \sum_{out} \dot{m} (h+ke+pe) -\sum_{in} \dot{m} (h+ke+pe) $$ Hence, $$\dot{Q} = \sum_{out} \dot{m} h -\sum_{in} \dot{m} h $$ So for convection, $$hA_c(T_h - T_o) = \dot{m}(h_2-h_1) = \dot{m}c_p(T_o-T_i)$$???? Why would ##T_i## be a constant but not ##T_o##??
  4. J

    Convection heat exchanger

    Thanks Chestermiller. The way I derived your expression is, $$\dot{Q_{in}} - \dot{Q_{out}} = \frac{d(mc(T_o - T_i))}{dt}$$ but there is no ##\dot{Q_{out}}## if you consider the inner chamber as the system and there is no heat loss to the surroundings. So, $$\dot{Q_{in}} = \frac{d(mc(T_o -...
  5. J

    Convection heat exchanger

    Hey Chestermiller, could you provide more insight into how you derived that equation? Reading online I've only seen the expression $$Ah(T-T_{\infty}) = -\rho Vc \frac{dT}{dt}$$ after googling transient heat convection transfers.
  6. J

    Convection heat exchanger

    Ah!!!! Thanks so much!
  7. J

    Convection heat exchanger

    I'm still not quite convinced. Why would ##T_h - T_0## be the overall temperature difference?? Would the "overall" temperature difference be the average temperature difference? Which is $$T_h - \frac{T_0 - T_i}{2}$$ ???
  8. J

    Convection heat exchanger

    Hello Chestermiller; really apologise I didn't fill out the homework template. What does the over heat transfer coefficient ##h_c## have anything to do with the temperature difference being ##T_h - T_o##? I would argue that the temperature difference used in ##q = h_c A \Delta T## should be...
  9. J

    Convection heat exchanger

    Hello guys, in the question attached, my understanding is that there is a heat transfer that heats the fluid from an initial at the input, to at the output. This heat transfer is via convection from walls of temperature . Firstly, . Because the walls are and the fluid is of a lower...
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