Multi-Stage Absorption Heat Pump Without Refrigerant Splitting
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Solution Overview
Problem
Multi-stage absorption heat pump cycles face efficiency losses and instability due to refrigerant stream splitting issues, which become exacerbated under varying operating conditions, leading to performance reductions and safety concerns.
Innovation Solution
The solution involves eliminating the refrigerant split by passing the entire flow through a heat exchanger where part evaporates, and then separating the vapor and liquid fractions, allowing the liquid fraction to be directed to the evaporator, thus self-adapting refrigerant quantity based on absorber load, eliminating the need for a splitter and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If refrigerant stream splitting is used in multi-stage absorption heat pump, then the cycle can operate at lower generator temperatures (about 50°C less than single effect), but the cycle efficiency is reduced to about one half of single effect cycle
Solution Approach 1:
The patent implements dynamic control of the refrigerant split ratio by varying the opening degrees of electronic expansion valves based on real-time detection of temperatures and pressures at different locations in the cycle. This allows the system to adapt to changing operating conditions and maintain optimal efficiency across a range of generator temperatures, resolving the contradiction between operating at lower temperatures and maintaining high efficiency.
2Device complexity
If a fixed geometry splitter is used for refrigerant division, then the system is simple in structure, but under operating conditions different from optimization, the splitter splits refrigerant differently in a manner not proportional to requirements, resulting in efficiency losses
Solution Approach 1:
The patent replaces the fixed geometry splitter with dynamic control elements (electronic expansion valves) that can adjust the refrigerant split ratio in real-time based on operating conditions. This dynamic adaptation allows the system to maintain optimal efficiency across varying thermal inputs, ambient temperatures, and thermal loads, eliminating the efficiency losses associated with fixed geometry splitters.
Solution Approach 2:
The patent implements a feedback control system that detects temperatures and pressures at multiple locations and uses this information to dynamically adjust the refrigerant split ratio. This closed-loop control ensures that the refrigerant distribution remains proportional to the actual requirements of the two branches under all operating conditions, preventing efficiency losses.
3Adaptability or versatility
If refrigerant flow rates and pressures vary under transient conditions, then the system responds to changing ambient temperature and thermal loads, but periodic oscillations and instabilities are triggered, making control problematic
Solution Approach 1:
The patent uses dynamic control of electronic expansion valves to actively manage refrigerant flow distribution under transient conditions. By continuously adjusting valve openings based on real-time sensor data, the system can respond to changing ambient temperatures and thermal loads without triggering oscillations or instabilities, maintaining both adaptability and stability simultaneously.
Solution Approach 2:
The patent implements feedback control that continuously monitors temperatures and pressures and adjusts refrigerant split ratios to prevent oscillations. This closed-loop system detects early signs of instability and corrects them by adjusting valve positions, thereby maintaining cycle stability even under rapidly varying operating conditions.
4Device complexity
If the refrigerant quantity fed to cool the absorber is insufficient, then the system structure remains simple, but absorption is incomplete and the extent of operative conditions is reduced
Solution Approach 1:
The patent implements dynamic control of refrigerant distribution to the absorber using electronic expansion valves that adjust opening degrees based on detected operating conditions. This ensures that the refrigerant quantity fed to cool the absorber is always sufficient for complete absorption, expanding the range of operative conditions while maintaining simple basic system structure.
Solution Approach 2:
The patent uses feedback from temperature and pressure sensors to dynamically adjust refrigerant flow to the absorber. This ensures that absorption is always complete by providing sufficient refrigerant quantity, thereby expanding the operational envelope of the system without requiring complex additional hardware.
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 stabilizes the cycle operation and increases efficiency under variable conditions, allowing the system to approach single-effect cycle efficiency even under conditions where double-effect cycles are typically less efficient, reducing the risk of oscillations and instability.
Implementation Method 1
passing the entire flow through a heat exchanger where part evaporates
Implementation Method 2
passing the entire flow through a heat exchanger
Implementation Method 3
absorption heat pump cycles
Data Source
Figure 1
Figure 2
AI summary
An absorption heat pump comprising a generator (2) or desorber which generates vapour from a first fluid fed to a first condenser (4), an evaporator (7) being provided downstream of the condenser, an outlet (7B) of the evaporator being connected by a third line (8) to an inlet of a mixer of a low pressure absorber (100) connected to a suction side of a pump (14) feeding solution to the generator, the generator comprising a poor solution outlet (2C) connected by a sixth line (19) provided with at least one lamination valve (30, 31) to a poor solution inlet feeding the absorber (100, 200-100). The second line (6) is brought into heat exchange contact with the low pressure absorber (100) and opens into a liquid/vapour separator (51) feeding the evaporator (7) via a third line (6A), the vapour outlet of the separator (51) opening into an intermediate pressure absorber unit (200).