Anonymous
Anonymous asked in Science & MathematicsEngineering · 1 month ago

Simple Thermodynamic Question? (Maybe)?

Hello, I hopefully have a simple thermodynic question.

I was taught that when two substances are in contact, heat transfer will happen until both are the same temperature, in equilibrium.

So with that being said, if you wrap a pipe in electrical heat tracing (the tracing wire only gets as hot as 60 degress celsius) and then wrap the pipe and tracing in insulation, how is it that if the heat tracing is forced to be on all the time, the pipe (well I guess technically everything under the insulation, not just the pipe) reaches over 60 degrees celsius, when the heat tracing should only go to 60 degrees celsius?

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  • 4 weeks ago

    There must be a controller in the heater unit. If it is going over 60 C then the controller is probably faulty.

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  • 4 weeks ago

    Heat tracing tape is rated to provide a certain amount of heat per unit of length. So it will produce that amount of heat. Unless it has a temperature controller it will reach equilibrium with its surrounding. In your case there is not sufficient information to actually determine what will happen.

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  • 1 month ago

    Although the heat tracing wire itself may get to 60C, its effect on the process pipe may be at a lower setpoint than that, to keep the heat flowing into the pipe.  You are correct, if the true temperature of the wire itself is 60C, then it cannot get over that temperature, unless the process pipe itself exceeds 60C.  But be careful, the rating of the heat tape may not be based on the temperature of the wire itself, that may be its design in certain specified situations, it may pay to get the specifications and determine what that is.

    And, in general, not all heat tracing is based on keeping water from freezing, I worked in a plant where boric acid solution piping had to be kept over 100F to keep it from solidifying.

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  • 1 month ago

    Heat tape (tracing) is generally designed to heat their pipe to at most 5 or 7 degrees C.  Perhaps the insulation is rated to 60 C but heat pipes do not get anywhere near 60C.  The purpose of heat tape is to keep the pipes from freezing which is 0 C.  60C heat tape makes no sense.  Heat will be lost to the outside as long as it is cooler than the temperature the pipe is being maintained at.

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  • 1 month ago

    I don't know what you mean by "heat tracing", I'll assume an electrical heat tape.

    Heat tape gets as hot as its surroundings allow, with electrical energy heating up it and the surroundings, and heat losses cooling it. The net is a temperature equilibrium at some temperature. 

    Usually there is a thermostat somewhere in the loop which shuts off the power when the temperature exceeds a set point.

    But bottom line, the temperature of the surroundings cannot exceed the temp of the heat tape itself, and in fact must be lower. 

    If the temperature gets to be over the setting, then the thermostat is defective. 

    And, heat tapes are usually set for about 40ºF, not 60º

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