The Hotline: 12/05/2005

Distributor Technology

COMMENT:
By Herman Krantz
Sun City, Calif.

I want to make readers aware of a technology developed in the late 1960s and early 70s that I believe is still viable today.

In those years, Rigidbilt Inc. developed a "box" type distributor for use primarily with ammonia coils using recirculated liquid and horizontal airflow. I, as vice president and engineer at Rigidbilt, along with Bob Lamprectt, then president at Rigidbilt, and Eugene Rytlewski, a consultant who spent 34 years with Westerlin and Campbell (the Chicago contracting office of York Corp.), were looking for uniform liquid distribution at varying liquid pressures and volumes, along with uniform distribution of hot gas for defrosting.

What evolved was a series of 3/8-inch O.D. steel tubes extending up inside a 2-1/2- by 3-1/2-inch rectangular steel tube with orifices in the tubes inside the rectangular box. The project included refinement in sizing, locating of the orifices, and internal construction.

After Rigidbilt used the distributor for a few years, Bill Richards of H.A. Phillips Co. (who was so extremely helpful to Rigidbilt in our ammonia work) started referring to our distributor as "Herman's Box Distributor." Thereafter, a number of contractors and mutual acquaintances referred to the distributor by the same name, and I, a young sales engineer, relatively new to the industry, was quite proud to have developed such a practical and useful adjunct to our coils.

By the time Bob and I retired from Rigidbilt in 1984, the company was using this distributor not only on ammonia coils, but also on a great many refrigerant coils because it was so simple, reliable, and trouble-free. By this time, many of our customers were asking to have the distributor on their equipment.

Rigidbilt used this distributor for about 15 years and the benefits to our company far exceeded our wildest expectations. Some of these benefits were:

From day one, we were fortunate and provided enough orifices and large enough tubes to avoid troubles.

A 3/8-inch-O.D. steel tube is relatively comfortable for handling and welding so we used 3/8-inch-O.D. tubes exclusively.

We used the same size tubes and the same orifices for ammonia, refrigerants, recirculating systems, TXV systems, and hot gas defrost systems.

We could build the distributor at our convenience, or we could wait until the coil is virtually complete, and avoid the problems in ordering the correct distributor, number, and size of tubes, orifice, flanges, connection size, etc., plus time for shipping and handling.

At times we needed to make changes to coils, and it was a simple matter to change the number of circuits, or even build a new distributor.

Our shop men quickly became familiar with the drilling and welding operations, so we rarely needed any extra training or supervision.

We never heard of, and never knew of, a problem with the distribution of the liquid or gas.

We never heard of, and never knew of, any orifices being plugged in use.

We always figured the pressure drop through the distributor was negligible or a few pounds at worst. One test we ran was with water at 5 psi, and we concluded that 5 psi with any liquid was more than adequate to feed any of our coil circuits even using 1-inch-O.D. tubes in refrigerant coils.

It was not necessary to keep distributor tubes of uniform length. This made it easier to fit and weld the distributor to the coil.

Separate connections for liquid and hot gas were often desirable; it was a simple matter to furnish two or even three separate connections.

When we started using this distributor, Bill Richards was talking about inserting a float valve between a thermal expansion valve and distributor to remove the flash gas and feed solid liquid into the coil. Rigidbilt, like other coil manufacturers, reduced their "Fl.-Recirc" ratings by about 15 percent for TXV rating. If we could eliminate the flash gas, coil manufacturers could increase their TXV ratings and have only one coil capacity rating: Fl.-Recirc-TXV. This would be a huge benefit to our entire industry. The configuration of this box distributor is well suited to such an operation with a minimum of labor and expense.

If you would like to discuss this further, you can contact me at hermkran76@mchsi.com.

Publication date: 12/05/2005

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