Calculations and Computer Analysis

For best results for this part of the project, copious calculations are necessary, as is extensive use of chemical engineering software.

 

Computer Calculations

Using chemical engineering knowledge gained through courses at IIT, the lengthy condenser calculations were feasible.

It was first important to determine the temperatures of both the air and water streams of the condenser.  The water stream in (spray water) was set at 30°C.  The resulting water stream out of condensed water and spray water was set at 70°C.  The air stream temperatures obviously matched those of the evaporator and were 85°C and 35°C for air in and air out respectively.  Using these temperatures the log mean temperature can be calculated using the following equations.

The humidity of the inlet and outlet are calculated using the following equation and the saturated vapor pressures of the air.  The overall pressure of the system is 1.0 atm. 

The evaporator analysis gives the volumetric air flow rate and the mass air flow rate as 65534 ft³/hr and 1731 lb_m/hr.  These were calculated using the above  humidity values and will be described in more detail in the evaporator section of the report.  The humid volume can then be calculated as:

Also necessary is the volumetric flow rate of the circulating (or spray) water.  Since this can easily be controlled as part of the operating conditions of the condenser, it was selected through trial and error and was ultimately set at 2.7 L/s (or 343.3 ft³/hr.)  Multiplying this value by the density of water gives the mass flow rate of circulating water was as 20630 lb_m/hr. 

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Condenser Design
General Spray Condensers
Specific Design Considerations