Ejector Heat Pump with Controllable Needle for Off-Design Efficiency
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Solution Overview
Problem
Ejector operation in HVAC&R systems deviates from the design point during off-design conditions, leading to performance degradation, particularly in applications with wide temperature ranges, necessitating the use of complex and costly bypass expansion valves.
Innovation Solution
A heat pump system with a controllable ejector and variable speed fan, controlled by a controller that adjusts fan speed and ejector needle based on refrigerant pressure or temperature, allowing seamless switching between heating and cooling modes without the need for parallel expansion devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ejector is used to improve COP, then system efficiency is improved, but system complexity increases due to need for bypass expansion devices
Solution Approach 1:
The ejector needle is made movable and controllable, allowing dynamic adjustment of the ejector's operation. The controller adjusts the needle position based on operating conditions (heating/cooling modes, temperature ranges) to optimize performance across different scenarios, eliminating the need for fixed bypass expansion devices
Solution Approach 2:
The system changes physical parameters (needle position, refrigerant flow distribution) based on operating conditions. By adjusting the ejector needle position and controlling refrigerant flow dynamically, the system adapts to different temperature ranges and modes, maintaining high efficiency without complex bypass devices
2Loss of energy
If ejector operates at design point, then performance is optimized, but adaptability decreases for off-design conditions
Solution Approach 1:
The ejector system is made dynamic through controllable needle adjustment. The system transitions from static design-point operation to dynamic adaptability, where the needle position and refrigerant flow are continuously adjusted based on real-time operating conditions, enabling optimal performance across heating modes, cooling modes, and various temperature ranges
Solution Approach 2:
The controller receives feedback from temperature sensors and pressure sensors to adjust ejector needle position and refrigerant flow. This closed-loop control enables the system to maintain optimal performance by continuously adapting to changing operating conditions, ensuring the ejector operates efficiently across its full range of applications
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
Enhances system efficiency by maintaining optimal performance across varying conditions, reducing complexity and cost by eliminating the need for bypass expansion devices.
Implementation Method 1
A primary or motive flow of high pressure refrigerant from the condenser enters the primary or motive port (inlet) and passes through the motive nozzle of the ejector where it accelerates. It exits the motive nozzle with a high velocity and generates low pressure area around the exit.
Implementation Method 2
A secondary or suction flow of refrigerant vapor from the evaporator is entrained (i.e., sucked) into the secondary or suction port (inlet) of the ejector and is thereby accelerated.
Implementation Method 3
High velocity motive flow refrigerant decelerates and mixes with accelerating suction flow refrigerant in the mixing section (mixer) of the ejector.
Implementation Method 4
After mixing, the two phase refrigerant mixture enters the diffuser of the ejector, decelerates thereby recovering pressure.
Implementation Method 5
The resulting two-phase refrigerant stream enters the separator where the vapor and liquid phases are separated.
Implementation Method 6
Vapor is sucked into the compressor where it is compressed and discharged to the condenser or gas cooler.
Implementation Method 7
In the condenser, the compressed high pressure, high temperature vapor is cooled and condensed.
Implementation Method 8
Liquid from the separator enters the evaporator after passing through an expansion valve
Implementation Method 9
Liquid from the separator enters the evaporator after passing through an expansion valve, evaporates and vapor flows to the suction port of the ejector.
Data Source
Figure 1
Figure 1A~1B
Figure 2
AI summary
A method for operating a heat pump (20; 300) includes operating in a cooling mode wherein heat is absorbed by refrigerant in the indoor heat exchanger (26) and rejected by refrigerant in the outdoor heat exchanger (24). The heat pump switches to operation in a heating mode wherein heat is rejected by refrigerant in the indoor heat exchanger, heat is absorbed by refrigerant in the outdoor heat exchanger, and there is an ejector (60) motive flow and ejector secondary flow. In the heating mode a refrigerant pressure (PH) or temperature (TL) is measured and, responsive to the measured refrigerant pressure or temperature, at least one of a fan speed is changed and a needle (132) of the ejector is actuated.