1.1 Advantages of falling film evaporators

The falling film evaporators have following advantages over flooded evaporators:


The falling film evaporators also have many advantages over vertical tubes evaporators such as:


It can be seen clearly that falling film evaporators have many advantages over submerged and vertical tubes evaporators but there is lack of heat transfer data at sub-atmospheric temperature. Particularly, below 323 K, there is no data available in the literature. This was one of the main motivations for this work.

## 2. Heat transfer review for falling film evaporators

An efficient design of falling film evaporators is important especially for food and desalination industries. Conventionally, the empirical and theoretical correlations available in the literature are employed for the heat transfer area estimation. Most of correlations are based on different refrigerants and at near atmospheric temperature. Only few correlations are available for pure water for 322 K and above saturation temperatures. Table 1 provides the detail of many researchers' work related to heat transfer correlations. It also highlighted the studies of different operational parameters impact on heat transfer.


Table 1.

Literature summary on heat transfer coefficient investigation and operational parameters impact.



 Reviewof heat transfer coefficient correlations for different evaporator designand operationconditions.
