Here are the governing relationships for the makeup flow rate, the evaporation and windage losses, the draw-off rate, and the concentration cycles in an evaporative cooling tower system:

A water balance around the entire system is:

                              M = E + D + W   

Since the evaporated water (E) has no salts, a chloride balance around the system is:

                     M (X_M) = D (X_C) + W (X_C)   = X_C (D + W)            

and, therefore:

                     X_C / X_m = Cycles = M / (D + W) = M / (M – E) = 1 + {E / (D + W)}

From a simplified heat balance around the cooling tower:

                      (E) = (C) (DT) (c_p) / H_V

Windage losses (W), in the absence of manufacturer's data, may be assumed to be:

            W = 0.3 to 1.0 percent of C for a natural draft cooling tower

            W = 0.1 to 0.3 percent of C for an induced draft cooling tower

            W = about 0.01 percent of C if the cooling tower has windage drift eliminators

Concentration cycles in petroleum refinery cooling towers usually range from 3 to 7.  In some large power plants, the cooling tower concentration cycles may be much higher.

Website Spotlight

Looking for another great engineering website?   Checkout XCalcs.com.  They feature a list of useful calculations online in real time from their site.   Calculations include beams, vessel, plates, pipes, and others.

New Category Available in ChE Links
Dr. Bernhard Spang has added a new category to ChE Links.  Stop by and visit some of the new sites listed under "Nanotechnology".   Some of the new sites include an Introduction to Nanotechnology, Friction at the Nano-Scale, What is Nanotechnology, and several others.

Overheard in the Online Forum

Learn How to Use BB Code to Enhance Your Posting
One of our loyal message board participates (Milton Beychok) has posted a guide to use BB code to properly format your messages.  Read it here.

Reboilers: Kettle versus Thermosiphon Designs

"I would like some guidance on the relative benefits of kettle vs. vertical thermosiphon reboilers in NGL (DeC3 and DeC4) service.  Specifically we are looking at a turndown of 4:1 and some are concerned that a thermosiphon would not turndown well.  I am unconviced as the drive mechanism is based on relative densities and would therefore (I think) be independent of flow through the exchanger. Alternatively does anyone forsee turndown issues with a kettle?"

Read the replies to this message

Software Spotlight

EZZE AIRE is a utility designed to replace (supplement) the Psychrometric charts used by Engineers and HVAC specialists in heating, drying and air conditioning design and operations applications.  Currently, to determine air properties one needs to know two properties to determine the other 5 properties by using a ruler to extrapolate their values on two paper psychrometric charts.   This is a very confusing and inconsistent means of determining values to use in your design or process calculations.  EZZE AIRE removes inconsistencies by transforming the two Psychrometric charts into a paperless electronic chart which with a few key strokes produces air property values quickly and with good reproducibility.   In addition, there are sample problems which cover the most common process and air conditioning applications solved using EZZE AIRE.   The interface is extremely user-friendly and can be previewed here.

When you're ready to get your copy of EZZE AIRE, you can purchase from the online store and download the software immediately.

Discounts on CE Credits

Did you know that you can get a 10% discount on a variety of online CE courses offered by RedVector.com?  Visit the CE Credit section of our online store for instructions.   Remember, don't put the course in your "basket", use the link provided with each course description to order from RedVector.com.

FREE Trade Publications

Sign up for our FREE Trade Publications.

Advertise with Us

Our traffic is booming!  Approximately 18,000 people around the globe receive our newsletter and nearly 80,000 unique visitors a month visit our site.  See our advertising options.