Which best describes the internal structure of a shell and tube type evaporator?

The internal structure of a shell and tube type evaporator is best described as being full of liquid refrigerant with a gas space at the top. In this design, the refrigerant enters the evaporator in a liquid state and absorbs heat from the surrounding environment or a secondary fluid, causing it to evaporate into gas as it passes through the tubes. The gas that forms then rises to the top of the evaporator, creating a gas space where the refrigerant vapor accumulates before exiting the evaporator to enter the compressor.

This configuration allows for optimal heat exchange, ensuring efficient thermodynamic performance. The presence of liquid refrigerant at the bottom helps maintain the necessary pressure and temperature conditions for proper evaporation. The separation of the liquid and vapor phases also aids in the efficient flow of refrigerant, ensuring that the system operates effectively and maintains the proper heat transfer characteristics.

In contrast, the other options do not accurately represent the operational principles or construction of a shell and tube type evaporator. A fully gas-filled system would not allow for the necessary heat exchange and evaporative cooling, while being partially filled or completely filled with chilled water would contradict the fundamental working principle of refrigerant evaporation in this type of equipment.