Variable speed pumping system with pressure independent control valves
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Solution Overview
Problem
Existing variable-speed HVAC pumping systems are inefficient due to reliance on differential pressure setpoints, which often result in excessive pumping pressure and energy waste, and require remote sensors that increase complexity and cost.
Innovation Solution
A variable-speed pumping system utilizing pressure-independent control valves (PICVs) that absorb pressure fluctuations, eliminating the need for remote sensors and maintaining steady fluid flow through internal differential pressure regulators, with a pump controller that adjusts pump speed to keep PICVs at the lowest end of their control range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If differential pressure setpoint control is used to maintain pumping pressure, then system pressure stability is improved, but energy consumption increases due to excessive pumping pressure
Solution Approach 1:
The system uses feedback from flow sensors to continuously monitor actual fluid flow through the heat exchanger and adjusts pump speed accordingly. This closed-loop control allows the pump to operate at the minimum speed necessary to meet demand, eliminating the energy waste associated with maintaining fixed differential pressure setpoints that exceed actual requirements.
Solution Approach 2:
The invention transitions from static differential pressure setpoint control to dynamic flow-based control. The pump speed is continuously adjusted based on real-time flow measurements, allowing the system to adapt to varying thermal loads and operate efficiently across different operating conditions rather than maintaining a fixed pressure target.
2Measurement precision
If remote differential pressure sensors are deployed to monitor system pressure, then pressure control accuracy is improved, but device complexity increases
Solution Approach 1:
The invention extracts the measurement function from remote differential pressure sensors and relocates it to flow sensors positioned at the pump outlet. By measuring flow directly at the source and using this information to control pump speed, the system eliminates the need for complex remote pressure sensing and differential pressure calculations across the heat exchanger.
Solution Approach 2:
The system uses flow rate as an intermediary parameter to achieve pressure control. Instead of directly measuring and controlling differential pressure across the heat exchanger, the invention measures flow at the pump outlet and uses this intermediate measurement to indirectly control the pressure conditions, simplifying the overall measurement and control architecture.
3Use of energy by moving object
If pump speed is reduced to decrease energy consumption, then energy efficiency is improved, but flow stability deteriorates
Solution Approach 1:
The system employs feedback control by continuously monitoring actual fluid flow with sensors and comparing it to the required flow demand. The pump controller adjusts pump speed in real-time based on this feedback, ensuring flow stability is maintained even as pump speed varies to optimize energy consumption across different operating conditions.
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 reduces energy consumption and operating costs by ensuring the pump operates at the lowest necessary speed to maintain desired flow, achieving significant savings compared to traditional systems.
Implementation Method 1
Each PICV includes an internal differential pressure regulator, which is designed to absorb increases in system pressure via a spring-loaded compartment while facilitating steady fluid flow conditions
Implementation Method 2
Each PICV includes an internal differential pressure regulator, which is designed to absorb increases in system pressure via a spring-loaded compartment
Data Source
AI summary
A system for managing the flow of fluids within a closed-loop system includes a pump controller and a variable-speed pump in communication with a conduit circuit including at least one one pressure-independent control valve (PICV). By using PICVs instead of conventional, two-way, two-way, pressure-dependent valves, the pump controller can monitor system needs and adjust the the speed of the variable-speed pump to more efficiently deliver pressure to the system without overshooting flow requirements, leading to less energy consumed and less cost incurred. A method method of variable-speed pumping including the use of PICVs is also disclosed.