Cooling Coil Recirculation Control to Prevent Laminar Flow
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Solution Overview
Problem
Heating and cooling systems with cooling coils face inefficiencies due to laminar flow, which reduces heat exchange and leads to inefficient cycling when chilled water flow decreases, causing a threshold condition between proper air cooling and non-cooling.
Innovation Solution
Incorporating a recirculating line with a pump and check valve, coupled with a variable frequency drive, to maintain optimal water flow through the cooling coil by adjusting the temperature differential and using temperature and humidity sensors to adjust the setpoints for valve control, ensuring efficient heat exchange across the coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If chilled water flow through the cooling coil is reduced, then energy consumption decreases, but heat exchange efficiency deteriorates and laminar flow occurs
Solution Approach 1:
The system dynamically adjusts water flow through the cooling coil using a recirculating line with a pump and variable frequency drive. The controller modulates the pump speed to maintain turbulent flow conditions while optimizing energy consumption, preventing the system from operating in the inefficient laminar flow regime that occurs at low flow rates
Solution Approach 2:
The recirculating line ensures continuous water circulation through the cooling coil, preventing flow interruption and maintaining consistent heat exchange efficiency. The system continuously monitors temperature differential and flow conditions to ensure optimal operation without allowing the flow to drop into the laminar regime
2Use of energy by stationary object
If chilled water flow through the cooling coil decreases, then system operation cost decreases, but cooling performance deteriorates due to threshold condition
Solution Approach 1:
The controller continuously monitors the temperature differential across the cooling coil and the water flow conditions. When the temperature differential indicates approaching the threshold condition or when flow rate decreases, the controller automatically adjusts the recirculating pump to increase flow and maintain turbulent conditions, ensuring reliable cooling performance while managing operating costs
Solution Approach 2:
The system proactively maintains optimal flow conditions before the threshold condition is reached. By continuously monitoring flow and temperature parameters, the controller adjusts the recirculating pump in advance to prevent the onset of laminar flow and threshold conditions, ensuring consistent cooling performance
3Loss of energy
If a recirculating line with pump and control system is added, then heat exchange efficiency is maintained, but device complexity increases
Solution Approach 1:
The recirculating pump serves multiple functions: it maintains turbulent flow through the cooling coil, enables dynamic flow adjustment based on operating conditions, and works with the variable frequency drive to optimize energy consumption. This multi-functionality justifies the added complexity by providing comprehensive control over heat exchange efficiency and energy usage
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 solution enhances the efficiency of the cooling coil by maintaining optimal flow and temperature differentials, preventing laminar flow and ensuring consistent cooling performance, thereby reducing energy consumption and improving system efficiency.
Implementation Method 1
chilled water circulates through coil 18, where an air/water heat exchange occurs, leading to air 18 forced through coil 14 being cooled and the supplied chilled water being warmed
Implementation Method 2
Incorporating a recirculating line with a pump and check valve
Implementation Method 3
coupled with a variable frequency drive, to maintain optimal water flow through the cooling coil
Implementation Method 4
Incorporating a recirculating line with a pump and check valve
Data Source
AI summary
A system for operating a cooling loop associated with a space and including at least one cooling coil and cooling fluid supply, the system including: a grain sensor positioned with respect to the space and providing a value indicative of the amount of moisture in the space; at least one pump fluidly coupled across the coil; at least one flow limiter fluidly coupled to the coil and limiting a flow of cooling fluid between the cooling fluid supply and the coil; and at least one controller electrically coupled to the flow limiter; wherein, the at least one controller selectively operates the flow limiter responsive to the value indicative of the amount of moisture in the space and the pump re-circulates cooling fluid independent of the cooling fluid supply dependently upon the flow limiter.