Staged Spray Heat Exchanger for Lower Water Use
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Solution Overview
Problem
Existing indirect evaporative cooling systems, such as the Oasis ™< system, consume significant amounts of water and lack efficient mechanisms for reducing water consumption, especially in cold weather conditions and during emergency backup scenarios.
Innovation Solution
A staged spray indirect evaporative cooling system with a heat exchanger assembly divided into sections, controlled by a microprocessor-based controller, that selectively uses nozzles to discharge coolant onto the tubes based on temperature conditions, integrating a mechanical cooling system for backup, and includes a sump with a pump to prevent freezing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous water circulation is used in indirect evaporative cooling systems, then cooling performance is maintained, but water consumption increases significantly
Solution Approach 1:
The heat exchanger is divided into multiple sections along the airflow direction, with nozzles positioned at specific locations in each section. This segmentation allows water to be applied only where needed for cooling, rather than continuously across the entire heat exchanger surface, thereby reducing overall water consumption while maintaining effective cooling performance.
Solution Approach 2:
The system uses intermittent water discharge through nozzles rather than continuous circulation. Water is sprayed periodically onto the heat exchanger tubes when cooling is needed, and the pump cycles on and off based on temperature conditions. This periodic action significantly reduces water consumption compared to continuous circulation systems.
2Temperature
If water is circulated in cold weather conditions, then cooling is provided, but freezing of coolant in the sump occurs
Solution Approach 1:
The system includes a heating element positioned in the sump that activates when ambient temperature drops below a predetermined threshold (e.g., 32°F or 0°C). This preliminary heating action prevents the coolant in the sump from freezing before it can cause system failure, ensuring reliable operation in cold weather conditions.
Solution Approach 2:
A temperature sensor continuously monitors the ambient temperature and provides feedback to the controller. When the temperature drops below the freezing point, the controller activates the heating element in the sump. This feedback mechanism ensures the coolant remains liquid and the system operates reliably in cold weather.
3Quantity of substance
If large water storage tanks are installed, then water supply for cooling is ensured, but system complexity and space requirements increase
Solution Approach 1:
Instead of using large storage tanks to ensure adequate water supply, the system employs a small sump combined with an intermittent pump operation strategy. The pump cycles on and off, drawing water from the small sump and replenishing it from the heat exchanger condensation and occasional top-off. This partial action approach provides sufficient water supply without requiring large storage capacity, thereby reducing system complexity and space requirements.
4Loss of substance
If staged spray control is implemented, then water consumption is reduced, but control system complexity increases
Solution Approach 1:
The controller adjusts water consumption by changing operational parameters: it monitors temperature conditions and activates nozzles in different sections of the heat exchanger based on the cooling demand. When ambient temperature is low, fewer nozzles are activated or they operate at lower duty cycles. This parameter-based control reduces water consumption without requiring complex control logic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces water consumption, enhances temperature control, and minimizes the need for large water storage tanks by staged water usage and integration with mechanical cooling, ensuring consistent cooling performance even in emergency situations.
Implementation Method 1
indirect evaporative heat exchanger with a heat exchanger assembly, a plurality of nozzles, a sump, at least one pump
Implementation Method 2
The at least one pump is configured to circulate water from the sump to the nozzles located in at least one section of the heat exchanger
Implementation Method 3
The temperature sensor is configured to detect a control temperature
Implementation Method 4
The indirect evaporative heat exchanger includes a heat exchanger assembly. The heat exchanger assembly includes at least one tube having a first end, a second end, and an outer surface
Data Source
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AI summary
A heat exchanger assembly, an indirect evaporative heat exchanger including the heat exchanger, and methods of operating the same. The heat exchanger assembly includes at least one tube, a plurality of sections, and a plurality of nozzles. The at least one tube is configured to (i) have a process fluid flow therethrough in a first direction and (ii) have a scavenger cooling medium flow over the outer surface of the tube in a second direction. The second direction intersects the first direction. The plurality of sections is aligned in the first direction. The plurality of nozzles are located above the at least one tube. At least one nozzle of the plurality of nozzles is (i) located in each of the plurality of sections and (ii) configured to selectively discharge coolant onto the portion of the tube in that section of the heat exchanger.