Engine valves (cp = 440 J/kg·K and r = 7840 kg/m3) are to be heated from 40°C to 800°C in 5 min in the heat treatment section of a valve manufacturing facility. The valves have a cylindrical stem with a diameter of 8 mm and a length of 10 cm. The valve head and the stem may be assumed to be of equal surface area, with a total mass of 0.0788 kg. For a single valve, determine (a) the amount of heat transfer, (b) the average rate of heat transfer, (c) the average heat flux, and (d) the number of valves that can be heat treated per day if the heating section can hold 25 valves and it is used 10 h per day.
Latent heat and phase change
A physical process in which a conversion among the basic states or phases of matter, i.e., solid, liquid, and gas takes place under the effect of a certain temperature and pressure is referred to as a phase change. Generally, the phase change of a substance occurs when heat transfer takes place between the substance and its surroundings. Based on the direction in which heat transfer takes place, different types of phase changes can occur.
Triple Point of Water
The branch of physics in which observer deals with temperature related properties is called thermodynamics.
Boiling Point of Water
Everyday examples of boiling is, boiling milk, heating water. One would have observed that when we heat water it goes through various stages and at one point bubbles show in water, and water keeps splashing with bubbles bursting, we in layman terms say that water is boiling.
Freezing Point of Water
In general, the freezing point of water is 0° Celsius, or 32° Fahrenheit. This is the temperature at which water will ordinarily change from its liquid state to its solid state (ice). However, there are certain conditions that can affect the freezing point of water. For example, a liquid may be supercooled or contain impurities so that it does not freeze at the ordinary freezing point.
Engine valves (cp = 440 J/kg·K and r = 7840 kg/m3)
are to be heated from 40°C to 800°C in 5 min in the heat treatment
section of a valve manufacturing facility. The valves have
a cylindrical stem with a diameter of 8 mm and a length of
10 cm. The valve head and the stem may be assumed to be of
equal surface area, with a total mass of 0.0788 kg. For a single
valve, determine (a) the amount of
rate of heat transfer, (c) the average heat flux, and (d) the
number of valves that can be heat treated per day if the heating
section can hold 25 valves and it is used 10 h per day.
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