It has been proposed to construct an air heater by placing a

It has been proposed to construct an air heater by placing a Cuprothal 49 strip inside a housing and passing air in parallel with the strip. The thickness of the strip is 2mm and has an electrical resistivity of 1.1410-6 m, a thermal conductivity of 21 W/mK, and an emissivity of 0.7. The objective is to provide air at a temperature of Tf=60°C under flow conditions that provide a heat transfer coefficient of 300 W/m2 K. The temperature of the housing is isothermal with the heated air. Although the melting point of the Cuprothal wire is approximately 1200°C, the material begins to undergo creep deformation at approximately 600°C. The housing is arranged such that there is a symmetry plane running down the center of the wire thickness.

a) (10 points) Based on this information, what is the maximum allowable current, I?

b) (6 points) If the system operates at 24V, what is the corresponding maximum length L of wire that can be used?

c) (4 points) What are some ways to improve the efficacy of the heater design?

Solution

The answer of following question is as follows.

The maximum allowable current is 56 ampere.

The maximum length is 7 m.