Water is to be boiled at sea level in a 30 -cm-diameter...

Name: Problem 39, Chapter 3: Thermodynamics: An Engineering Approach
Uploaded: 2020-07-08T23:56:02-08:00
Duration: 1 min 21 s
Channel: Mayukh Banik
Description: Water is to be boiled at sea level in a 30 -cm-diameter stainless steel pan placed on top of a 3 -kW electric burner. If 60 percent of the heat generated by the burner is transferred to the water during boiling, determine the rate of evaporation of water.

Water is to be boiled at sea level in a 30 -cm-diameter stainless steel pan placed on top of a 3 -kW electric burner. If 60 percent of the heat generated by the burner is transferred to the water during boiling, determine the rate of evaporation of water.

Key Concepts

Latent Heat of Vaporization

Latent heat of vaporization refers to the amount of energy required to convert a unit mass of a liquid into vapor without a change in temperature. This concept is crucial in phase change problems such as boiling, where the energy added does not increase the temperature but instead facilitates the transformation from liquid to gas.

Energy Transfer and Power

In thermodynamics, the power rating of a heat source indicates the rate at which energy is supplied. When considering practical applications, not all the generated energy is effectively used; only a fraction—determined by system efficiency—is transferred to the medium being heated. This concept is essential for calculating how much energy is actually available for processes like evaporation.

Heat Transfer Efficiency

Heat transfer efficiency describes the proportion of energy from a source that is successfully delivered to the target substance. In practical setups, various losses occur, and only a percentage of the input energy contributes to heating or phase transitions. Understanding and applying this efficiency factor is key when calculating real-world energy usage and the resultant physical changes.

Conservation of Energy in Phase Change Processes

The principle of conservation of energy states that the total energy input into a system is equal to the energy stored or used within that system. In problems involving phase changes, like boiling water, this energy is predominantly used to overcome the latent heat requirement rather than raising the temperature of the substance. This balance is fundamental for analyzing energy usage during evaporation.

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