1. A refrigerant at TR is flowing through a tube of radius RT. Surrounding the t
ID: 2074429 • Letter: 1
Question
1. A refrigerant at TR is flowing through a tube of radius RT. Surrounding the tube is water at its freezing temperature (TL > TR). The ice grows very slowly compared to the heat transfer rate within the ice.
a. What is the temperature distribution within the ice layer?
b. Assuming that the initial thickness of the ice is R0, how long will it take for a 50% growth in the ice layer?
2. A cylindrical candle is lit. As it burns, it provide a constant amount of heat to the wax. The wax beneath it melts (and instantaneously evaporates off) at Tmelt. The base of the candle is set at the Tambient. Assume that the candle wax conducts heat instantaneously.
a. Air is not an insulator and flows around the candle. Determine the temperature distribution within the candle wax. The heat transfer coefficient is ‘h’.
i. Hint: T = f(r,z,t) but the average radial temperature is only a function of z and t (i.e., Tavg = f(z,t)). Figure out how to convert the heat equation to only be a function of Tavg. Think about bulk properties and integral averages.
Explanation / Answer
Ans 1.a.
Measurements of the thermal coductivities of the frozen layer of aqueous binarysolutionss have been performed using the transient hot-wire method. Solutions of ethylene glycol and sodium chloride were utilized as the testing fluids, and they were frozen up in the test section in which the platinum wires 40 micro meter in diameter and 170 mm in length were strung. Measurements were carried out under euilibrium at a varity of both the initial concentration of the solution and the temperature of the frozen layer. The expression of the thermal conductivity of the dendritic ice layer was favorably assessed with the Licheneker's model by introducing the solid fraction under an assumption of the equilibrium within the range of parameters examined.
Ans 2
A cylindrical candle is lit. As it burns, it privide a constant amount of heat to the wax. The wax benethe it melt (instantaneously evaporates off) at Tmelt . The base of the candle is set the Tambient . Assume that the distribution through out the candle must be taken into consideration.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.