COOLING WATER PROCESS CONTROL SYSTEM

Abstract

A cooling system uses a closed circuit cooling tower in series with a chiller to either lower the chiller operating point or completely cool the chill water without use of the chiller, depending on weather conditions. The process and system expands the entire function of the cooling process with a control system design that examines the power consumed by all the devices of the system, the actual load being introduced into the system, water temperatures, and weather conditions, and makes decisions based on performance criteria through the control device's program algorithms.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of U.S. provisional application number 61/755,433, filed Jan. 22, 2013, the contents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to cooling processes and systems and, more particularly, to the use of closed circuit cooling tower to either lower the chiller operating point or completely cool without use of the chiller, depending on weather conditions.

Water chillers are often used to provide mechanical cooling to a building, data center, industrial process, or the like. Conventional chillers provide mechanical cooling by removing 100% of the heat load from the water. These systems have heat exchangers and require multiple pumps. The conventional systems can create delta temperature losses that decrease overall system efficiency.

As can be seen, there is a need for an improved cooling process and system that can selectively take advantage of water tower cooling when feasible.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a cooling system comprises one or more chillers; one or more closed circuit cooling towers in series with the one or more chillers; and a controller operable to utilize the closed circuit cooling towers as a pre-cooling device to lower an operating point by reducing a heat load to the one or more chillers, the controller further operable to use only the one or more closed circuit cooling towers, shutting down the one or more chillers, when the heat load can be removed by the one or more closed circuit cooling towers.

In another aspect of the present invention, a method for operating a cooling system comprises utilizing one or more closed circuit cooling towers in one of three operation states, a first operation state where the closed circuit cooling tower is used as a pre-cooling device to lower an operating point by reducing a heat load of chill water to one or more chillers, a second operation state where the closed circuit cooling tower is used to remove the heat load from chill water and the chill water is used directly to a load, without using the one or more chillers, and a third operation state where the closed circuit cooling tower is used to adjust a water flow to have the cooling tower create a false load and the chiller is adjusted to a less kilowatt per ton (kW/T) operating point; and controlling the operation state of the one or more chillers with a controller.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWING

The Figure is a schematic representation of a cooling water process control system according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

Broadly, an embodiment of the present invention provides a cooling system using a closed circuit cooling tower in series with a chiller to either lower the chiller operating point or completely cool the chill water without use of the chiller, depending on weather conditions. Conventional water side economizers do not use the tower water in series with the chillers. The process and system of the present invention expands the entire function of the cooling process with a control system design that examines the power consumed by all the devices of the system, the actual load being introduced into the system, water temperatures, and weather conditions, and makes decisions based on performance criteria through the control device's program algorithms.

Referring now to the Figure, the process and system of the present invention uses cooling towers 12 as energy balance control, via the control system, to either (1) divert the return water flow 20 from the load (not shown) through a tower 12 first, then through the evaporator of the chiller 10, effectively reducing the load to the chiller(s), or (2) divert the return water flow 20 from the load through only the tower 12 to cool the entire load, without using the chiller(s) 12, by by-passing the chillers(s) 12 while monitoring all data points to make operating decisions.

A process controller 14 used in the present invention can assess the kilowatt per ton of the chiller(s), pumps, fans, water temperature, and the like, and, if the load reduces to a point that the cost to operate the chiller(s) is more kilowatts per ton (kW/T), then the controller will adjust the water flow to have the towers create a false load, adjusting the chiller(s) to a less kW/T operating point that, in most cases, is a higher capacity percentage, but lower kW/T. When conditions are correct, the chiller(s) can be taken out of operation, along with condenser water pumps, and only the towers and the chill water pumps (not shown) will operate and, at reduced kW/T load points, while controlling the water results to the load. Using the closed circuit cooling towers allows for precise water chemistry treatment to allow the water to be used as a direct coupled process to all devices.

The Figure shows an exemplary wall 22 that separates the inside from the outside. This wall 22 can be located at various locations and is not meant to be disposed adjacent to the chiller 10 and the cooling towers 12.

Magnetic chillers 10 can be used as the primary cooling source, until weather conditions allow, then the cooling towers 12 can act as a pre-cooling device to lower the operating point of the chiller 10 by reducing the heat load to the chiller 10, allowing the chiller 10 to operate at its most efficient point as possible at all times. Kilowatt meters can be used to reflect the operating point and control systems can be used to determine the positions of the valves V1-V15 to separate the closed circuit cooling towers 12 to do different functions for condenser heat rejection and evaporator pre-cooling heat reduction to the chillers 10.

In some cases, the cooling towers 12 can be used to completely cool the chillers 10, where the condenser pumps 24 can be turned off, but left in a rapid restart mode, if needed to be turned back on to handle a higher heat load, or if weather conditions change such that the cooling towers 12 can no longer handle the required heat load.

The system of the present invention includes one or more magnetic chillers (one is shown in the Figure, but any number can be used, depending on the system design, heat load needs, and the like). Other styles of chillers can be used instead of or in addition to magnetic chillers. The system further includes one or more closed circuit cooling towers 12. The Figure shows two cooling towers 12 connected in parallel with each other (and in series with the chiller); however, the system could use any number of cooling towers.

The system of the present invention also includes various measurement and flow control devices, such as actuator controlled valves V1-V15, wet bulb calibrated sensors, insert water sensors, kilowatt meters, pressure transducers, variable frequency drives (for tower fans, condenser and chill water pumps, for example), piping special configurations and control engineering programming data with fail safe devices for maintaining normal operating demand.

The valves V1-V15 can be used to provide the most efficient operation of the system. For example, the valves can be used to control whether chill water or condenser water flows through each of the cooling towers 12. The valves V1-V15 can also be used to control whether chill water passes through the chiller 10, or if the cooling towers 12 alone provides sufficient cooling to deliver this cooling water chilled water directly to the load.

To use the present invention, heat load requirements and safety factors can be established and the optimal magnetic chillers (or other chiller type) and closed circuit cooling towers can be chosen for the application. Climate performance data can be plotted and piping can be configured to perform all functions, from the towers to the chiller, both evaporator and condenser functions, together and separately. Valves can be used to actuate against the pressure differential of the system pumps. Wet bulbs, entering and leaving water temperature, pressure differentials, and kW/T data for all functions can be gathered to control the process function for the most efficiency at all times. Transducers can be used to operate variable frequency drives (VFDs) to control pumps and kilowatt meters can be used to monitor all devices for comparison to the reflected load gathered by flow stations reporting the load conditions.

The system and process of the present invention can be used in office, data centers, and manufacturing industries on a broad spectrum. The system and process of the present invention can be easily adapted to various real world needs and can be scaled accordingly. The system and process of the present invention can reduce kW/T loads, effectively reducing operating cost. Combined with potential load shed methodology, the peak load reduction is a viable solution for the customer to avoid the higher demand load kilowatt-hour cost.

In some embodiments of the present invention, a geothermal addition and a dedicated reheat system addition can be used to enhance the process and provide heating water. In some embodiments, magnetic bearing chillers can do the reheat function via a separate water loop for the heating water and supplemental piping to the chill water loop. The geothermal loop can help remove heat from the system, both condenser water and chill water, to increase the useful hours of supplemental cooling.

It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

1. A cooling system comprising:

one or more chillers;

one or more closed circuit cooling towers in series with the one or more chillers; and

a controller operable to utilize the closed circuit cooling towers as a pre-cooling device to lower an operating point by reducing a heat load to the one or more chillers, the controller further operable to use only the one or more closed circuit cooling towers, shutting down the one or more chillers, when the heat load can be removed by the one or more closed circuit cooling towers.

2. The cooling system of claim 1, further comprising a plurality of actuator driven valves receiving commands from the controller to control flow of condenser fluid and chill fluid through the cooling system.

3. The cooling system of claim 1, wherein the controller receives input from a plurality of sensors to determine an operation state that provides optimal energy efficiency.

4. The cooling system of claim 1, wherein the plurality of sensors include wet bulbs, entering and leaving water temperature sensors, pressure differential sensors, and weather condition sensors.

5. A method for operating a cooling system, comprising:

utilizing one or more closed circuit cooling towers in one of three operation states, a first operation state where the closed circuit cooling tower is used as a pre-cooling device to lower an operating point by reducing a heat load of chill water to one or more chillers, a second operation state where the closed circuit cooling tower is used to remove the heat load from chill water and the chill water is used directly to a load, without using the one or more chillers, and a third operation state where the closed circuit cooling tower is used to adjust water flow to have the cooling tower create a false load, allowing the one or more chillers to be adjusted to a less kilowatt per ton (kW/T) operating point; and

controlling the operation state of the one or more chillers with a controller.

6. The method of claim 5, further comprising controlling a plurality of actuator driven valves that receive commands from the controller to control flow of condenser fluid and chill fluid through the cooling system.

7. The method of claim 5, further comprising receiving input from a plurality of sensors to determine an operation state that provides optimal energy efficiency.

8. The method of claim 7, wherein the plurality of sensors include wet bulbs, entering and leaving water temperature sensors, pressure differential sensors, and weather condition sensors.