Absorption Heat Pump Modulation With Intermediate Solution Heat Exchange
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Solution Overview
Problem
Existing absorption heat pumps face efficiency drops when generator power is modulated, due to high refrigerant concentration leading to flash evaporation and reduced heat recovery, and existing modulation methods are complex, costly, and prone to inefficiencies.
Innovation Solution
Incorporating a lamination valve with an intermediate heat exchanger to manage pressure and maintain efficient flow distribution, reducing flash evaporation and enhancing heat exchange between poor and rich solutions, along with optional refrigerant injection to adjust ammonia concentration and reduce rectifier load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If fixed throughput throttling members are used to modulate generator power, then burner power can be reduced, but solution concentration increases causing flash evaporation and reduced heat recovery
Solution Approach 1:
The patent replaces fixed throughput throttling members with variable flow restrictors that can dynamically adjust their opening degree to modulate poor solution flow. This dynamic adjustment maintains optimal solution concentration across different burner power levels, preventing flash evaporation and ensuring efficient heat recovery even at reduced power levels down to 20% of rated power
Solution Approach 2:
The invention changes the flow parameters of the poor solution by using variable flow restrictors that adjust the flow rate based on operational conditions. This parameter control prevents the concentration increase that leads to flash evaporation, maintaining stable heat exchange efficiency throughout the modulation range
2Reliability
If modulating valves are used to control poor solution flow, then cycle operating parameters can be maintained under optimum conditions, but device complexity and cost increase
Solution Approach 1:
The variable flow restrictors are designed to automatically adjust poor solution flow based on inherent pressure and flow conditions without requiring external actuators or electronic controls. This self-regulating mechanism maintains optimal cycle operating parameters while avoiding the complexity of additional actuators and control systems
Solution Approach 2:
The variable flow restrictors act as passive intermediary devices that mediate between the generator and absorber, automatically balancing poor solution flow to maintain optimal operating conditions without requiring active control systems or additional mechanical actuators
3Power
If low liquid flow is achieved through valve modulation, then generator power is reduced, but heat exchanger efficiency falls to very low values
Solution Approach 1:
The patent applies different flow control strategies to different parts of the system: variable flow restrictors are specifically positioned in the poor solution line to maintain adequate flow velocity through heat exchangers, while allowing overall system power to be modulated. This localized flow management ensures heat exchanger surfaces remain properly wetted even at reduced power levels
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
Achieves improved cycle efficiency by maintaining proper flow distribution and preventing flash evaporation, resulting in up to 35% efficiency improvement during modulation, with reduced system complexity and cost.
Implementation Method 1
enabling a pressure reduction from generator pressure to an intermediate pressure value
Implementation Method 2
there is an intermediate heat exchanger (40) enabling heat to be exchanged between the poor solution present in the line (19) and the rich solution
Implementation Method 3
enabling heat to be exchanged between the poor solution present in the line (19) and the rich solution flowing through the line (18) from the absorber (10) and directed to the desorber (2)
Implementation Method 4
an absorber (10) in which ammonia, originating from an evaporator (7), is absorbed in a rich solution
Implementation Method 5
a generator (2) or desorber presenting a finned gas burner (35), which feeds a conventional plate column (36)
Implementation Method 6
The rectified vapour outlet of the generator is connected via a first line (3) to a condenser (4) of conventional type
Data Source
Figure 1
AI summary
An absorption heat pump in which to improve heat efficiency when under desorber power modulation conditions, heat is exchanged between the rich solution, before it enters the desorber, and the poor solution withdrawn from the desorber, before this poor solution is fed into the desorber.