# What will happen to the heat input of the two-phase system?

• nesca
In summary, the conversation discusses the process of increasing the temperature of a half-filled tank of low boiling point liquid in a dry oven with a fan to evenly distribute the temperature. After reaching the boiling temperature, the tank is tightly sealed and the pressure increases due to evaporation. The question arises whether heat convection can be ignored in calculating the heat input, and if the equation Q=mcΔT can be used. The conversation also addresses how to determine the mass and specific capacity if the density and specific capacity of the liquid vary with temperature. In the case where there is no information on vapor properties, it is suggested to assume an ideal gas and calculate its properties. The conversation also touches on determining the heat of evaporation, which can
nesca
If I have a tank half-filled with low boiling point liquid at ambient temperature, then this tank is placed inside dry oven whose temperature is kept to be around 5℃ above the liquid boiling temperature. A fan is placed inside the dry oven as an effort to make temperature distribution even or at least minimize large gap to happen. Because of this the liquid temperature is increased, yet there is no bubble developed, or in other words there is no liquid bulk motion inside the tank.

After boiling temperature is reached, the tank is tightly sealed, thus the pressure is increased due to liquid evaporation.

In this case, to calculate heat input, is it okay to ignore heat convection both in liquid and gas and focus with heat conduction only?

Is the equation below can be used for heat input calculation?

Q=mcΔT

What if the density and liquid specific capacity vary with temperature? How to determine the mass and specific capacity?

If the gas phase is equal to liquid vapor and there is no information about vapor properties, what is the best way to at least obtain the density, thermal conductivity, and heat capacity for the gas phase?

What about the heat of evaporation?

anorlunda
mjc123 said:
What about the heat of evaporation?
If I'm not mistaken, to determine the heat of evaporation, we have to obtain internal energy of the system, and to do it ones should know the heat input of the system, shouldn't they?

No, if the system reaches equilibrium, the liquid will evaporate either until it is all vapour, or until the vapour pressure equals the equilibrium vapour pressure at the oven temperature (depending on how much liquid there is and the volume of the oven). You can work out how much liquid evaporates, and knowing the molar (or specific) heat of vaporisation, you can work out the heat input for vaporisation.
If you have no information on vapour properties, you can as a first approximation assume it's an ideal gas and calculate what its properties would be.

nesca

## 1. What is a two-phase system?

A two-phase system is a thermodynamic system that contains two distinct phases, such as liquid and gas, coexisting at the same temperature and pressure.

## 2. How does heat input affect a two-phase system?

The heat input into a two-phase system can cause a change in the state of the system, such as a phase transition or an increase in temperature.

## 3. What happens to the heat input during a phase transition in a two-phase system?

During a phase transition, the heat input remains constant as the energy is used to break or form intermolecular bonds, rather than increasing the temperature of the system.

## 4. Can the heat input of a two-phase system be controlled?

Yes, the heat input of a two-phase system can be controlled by adjusting the temperature or pressure of the system. This can be done through external heat sources or by manipulating the system's surroundings.

## 5. What factors influence the heat input of a two-phase system?

The heat input of a two-phase system is influenced by the system's temperature, pressure, and phase equilibrium. It can also be affected by external factors such as heat transfer, work being done on the system, or changes in the system's surroundings.

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