scope:

This test code applies to all heat rejection equipment, open circuit, mechanical and natural draft, which uses water evaporation. It includes all wet and combined wet and dry (parallel or series paths) heat rejection equipment. Closed circuit fluid coolers and adiabatic fluid coolers (e.g., precooling of ambient air dry bulb temperature), which contain two separate fluid circuits, are not covered by this test code but will be covered by a supplement in the future. The equipment being considered is the entire cooling system consisting of the structure (individual cell) with the heat and mass transfer surface (fill media and/or other exchanger media), water distribution and collection system, and mechanical equipment in the case of a mechanical draft equipment.

The first part of this test code describes the standard test procedures, operating conditions of the heat rejection equipment and the instrumentation necessary to measure the evaporative water consumption from wet-dry heat rejection equipment with repeatable and consistent results.

The second part of this test code describes a standard method to compute the evaporative water consumption from an all wet base system as the benchmark. A stand-alone calculation tool (in Excel) has been developed to standardize and speed up the calculation process. The result of the benchmark calculation is used to evaluate the water savings of different wet-dry technologies.

Purpose

The cooling industry has developed a variety of wet-dry heat rejection systems that aim to conserve water compared to a conventional all wet evaporative cooling equipment. These wet-dry systems typically combine dry (sensible) cooling with evaporative (latent) cooling, providing less water usage than a conventional all wet evaporative system. They use water evaporation either directly in the cooling process, or to pre-cool the ambient air.

Every wet-dry system design has different water saving potentials, costs, auxiliary energy demands, water chemistry requirements, reliability considerations, and space requirements. A potential purchaser must evaluate the viability of a particular wet-dry system using their site requirements, economic factors, and experience. This test code provides a method to calculate water consumption from a benchmark all wet cooling equipment and additional methods to verify the water consumption by laboratory or field measurements.

The purpose of this code is two-fold:

To provide standard test procedures to measure the evaporative water consumption from wet-dry heat rejection equipment with repeatable and consistent results. The results obtained can be used to demonstrate compliance with the predictions and / or guarantees offered by the manufacturer, and compliance with regulatory requirements.

To provide a standard method to compute the evaporative water consumption from an all wet base system as the benchmark. The result of the benchmark calculation is used to evaluate the water savings of different wet-dry technologies.