Ejector Heat Pump with Variable Needle Control for Adaptive Operation
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Solution Overview
Problem
Ejector operation in heat pumps deviates from the design or optimum operating point in various applications, leading to diminished performance, particularly in mild winter conditions where the potential work recovery from the high-pressure motive flow is low, resulting in increased system complexity and cost when a parallel expansion valve is utilized.
Innovation Solution
A method and system for operating a heat pump that switches between cooling and heating modes, using an ejector with a controller to adjust fan speed and actuate a needle based on refrigerant pressure or temperature measurements, eliminating the need for a parallel expansion device by optimizing ejector operation and airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a parallel expansion valve is utilized to bypass the ejector in mild winter conditions, then the system can operate in low work recovery conditions, but the system complexity and cost increase
Solution Approach 1:
The ejector nozzle area is made variable through the use of a needle valve that can dynamically adjust the nozzle cross-sectional area. This allows the ejector to adapt its performance characteristics to match varying operating conditions, enabling it to maintain effective operation across a wide range of work recovery potentials without requiring a parallel expansion valve bypass system
Solution Approach 2:
The invention changes the physical parameter of the ejector nozzle area from fixed to variable. By controlling the needle valve position, the nozzle area can be adjusted to optimize the ejector's entrainment ratio and pressure lift ratio under different operating conditions, particularly in mild winter conditions where work recovery potential is low
2Adaptability or versatility
If the ejector operates away from the design or optimum operating point, then the system can handle wide range of applications, but the cycle performance improvements diminish
Solution Approach 1:
A control system continuously monitors the actual operating conditions of the heat pump and adjusts the needle valve position accordingly. This feedback mechanism ensures that the ejector operates at or near its optimal performance point across a wide range of applications by dynamically matching the nozzle area to the current operating conditions
Solution Approach 2:
The variable nozzle area enabled by the needle valve provides dynamic adaptability that allows the ejector to maintain high performance across diverse applications. The system can transition from fixed-design operation to dynamic operation where the ejector characteristics are continuously optimized based on actual 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 enhances the performance of heat pumps by maintaining efficient operation across different conditions without the need for additional expansion devices, reducing system complexity and cost while improving the coefficient of performance.
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
After mixing, the two phase refrigerant mixture enters the diffuser of the ejector, decelerates thereby recovering pressure.
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.