Evaporative Cooling COC Control Using Discrete Refill and Drain Events
Solution Overview
Problem
Evaporative media systems in HVAC systems face challenges in controlling cycles of concentration (COC) effectively, leading to scaling issues due to varying water impurity concentrations, with existing methods either wasting water or causing fouling, and requiring additional sensors like conductivity meters for accurate control.
Innovation Solution
A COC control process involving discrete refill and drain events, where the system maintains a target COC value by executing a series of refill and drain operations, with each event involving the opening and closing of valves to add or remove water in a controlled manner, ensuring the COC is maintained within set limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant bleed rate is used to drain water, then scaling is controlled, but water is wasted due to high bleed-off rates and resulting low COC
Solution Approach 1:
The system transitions from a constant bleed rate to a dynamic bleed rate that adjusts based on actual evaporation rates and cooling demand. The controller continuously monitors system conditions and modifies the drain valve opening duration to maintain optimal COC, preventing both water waste and scaling.
Solution Approach 2:
The system implements feedback control by monitoring cooling demand and evaporation rates, then adjusting the bleed rate accordingly. The controller uses this feedback to calculate the appropriate drain duration that maintains target COC while minimizing water waste.
2Ease of operation
If drain events occur at user configurable time intervals, then operation is simplified, but COC control accuracy deteriorates due to varying conditions and cooling demands
Solution Approach 1:
The system replaces fixed time-interval draining with feedback-driven control that continuously monitors evaporation rates and cooling demand. This allows the system to automatically adjust drain timing and duration to maintain accurate COC control despite varying operating conditions.
Solution Approach 2:
The system transitions from static time-based scheduling to dynamic condition-based scheduling. The controller adjusts drain event timing and duration based on real-time monitoring of evaporation rates and cooling demand, maintaining COC accuracy across varying conditions.
3Measurement precision
If conductivity meter is used to sense water conductivity, then COC control improves, but device complexity increases and additional sensors are required
Solution Approach 1:
The system uses evaporation rate and cooling demand as intermediary measurements to infer COC status. Instead of directly measuring conductivity, the controller calculates required drain duration based on these intermediary parameters, achieving COC control without additional conductivity sensors.
Solution Approach 2:
The system replaces the need for conductivity meters (electrical measurement devices) with a control system that uses evaporation rate calculations and timing-based control. This substitutes complex electrical sensing with simpler mechanical/timing-based control logic.
4Measurement precision
If bleed rate is adjusted to match output, then COC maintenance improves, but water waste increases due to varying bleed-off rates
Solution Approach 1:
The system uses dynamic bleed rate adjustment based on actual evaporation rates rather than constant or output-matched rates. The controller calculates the precise drain duration needed to maintain target COC, optimizing the balance between COC maintenance and water conservation.
Solution Approach 2:
The system changes the control parameter from bleed rate (flow rate) to bleed duration (time-based control). By controlling how long the drain valve remains open rather than how fast water flows, the system achieves better COC maintenance with reduced water waste.
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
This approach allows for precise control of COC, preventing scaling while minimizing water waste, and adjusts dynamically to changing conditions, ensuring efficient operation of evaporative media systems.
Implementation Method 1
As air passes through the wetted media, water evaporates by taking energy from the air to vaporize the water
Implementation Method 2
This type of a process is often referred to as adiabatic cooling
Data Source
AI summary
A cycles of concentration (COC) control process and system for an evaporative media cooling system having a water storage tank in fluid communication with a drain valve and a refill valve is disclosed. In one step, the COC control process includes the step of executing a plurality of discrete refill events to maintain a level or volume of water within the storage tank. In another step, the COC control process includes the step of executing a discrete drain event, equaling the volume of a refill event, after a discrete refill event has been executed when necessary to maintain a target cycles of concentration value of the water within the storage tank. In one embodiment, a discrete drain event is executed when the number of refill events is greater than or equals a target cycles of concentration of the water in the storage tank.