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    Hey guys, I noticed that in the Rayleigh flow line in the subsonic part.. while heating the flow it reaches a point where it suddenly drops temperature but entropy still rises. any explanation ?
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    (Original post by namehereplease)
    Hey guys, I noticed that in the Rayleigh flow line in the subsonic part.. while heating the flow it reaches a point where it suddenly drops temperature but entropy still rises. any explanation ?
    this is an educated guess but:

    Entropy is defined as:

    ds = dq/T

    where T is the static temperature NOT total temperature.

    As you heat the fluid the total temperature of the fluid is increasing (i.e. dynamic temp +static temp) but the static temperature term itself will be very different because of the layers in the fluid itself, so obviously some parts of the fluid are hotter than others (just like when you warm up cold tea it can be kinda cold in some areas yet hot in other areas but overall you generally tend to have more hot areas than cold thus total entropy is increasing indicating energy loss).
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    I think i found the answer.. it is about the stagnation temperature between the 2 Mach numbers where it shows it is cooling.. speed of the flow accelerates faster than the heat added.. so the ratio of the static temperature to stagnation drops while increase in entropy continues. so this shows a drop in temperature which is not correct.

    thank you anyway
 
 
 
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