Liquid-Desiccant Heat Pump Dehumidification With Pre-Cooling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Heat pumps are inefficient in latent cooling and require high desiccant flooding rates and large pumps, leading to increased energy consumption and air-side pressure drops, while existing liquid-desiccant air conditioners face geometrical and operational limitations that reduce performance and increase capital costs.
Innovation Solution
A liquid-desiccant air conditioning system with an adiabatic absorber and desorber that uses a porous bed of contact media wetted with liquid desiccant, where the desiccant is exchanged between the absorber and regenerator, and a liquid-to-liquid heat exchanger is used to pre-cool and pre-heat the desiccant, optimizing desiccant flow rates and reducing thermal energy transfer to the air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If heat pumps are used for latent cooling by cooling air below dewpoint temperature, then dehumidification is achieved, but energy is wasted due to overcooling and reheating
Solution Approach 1:
A liquid desiccant is introduced as an intermediary substance between the air streams. The desiccant absorbs moisture from the process air in the absorber and releases it to the cooling air in the regenerator, enabling dehumidification without cooling air below dewpoint temperature and eliminating the need for reheating
Solution Approach 2:
The invention changes the operating parameters by using liquid desiccant concentration and flow rate as control variables instead of air temperature. By adjusting desiccant parameters, the system achieves dehumidification while maintaining air temperature above dewpoint, avoiding energy waste from overcooling and reheating
2Productivity
If existing liquid-desiccant air conditioners are used, then dehumidification is achieved, but high desiccant flooding rates and large pumps are required, increasing energy consumption
Solution Approach 1:
The invention optimizes desiccant flow parameters by using a heat exchanger to pre-cool the desiccant before it enters the absorber. This temperature optimization increases the desiccant's moisture absorption capacity, allowing lower flow rates to achieve the same dehumidification performance, thereby reducing pump energy consumption
Solution Approach 2:
The heat exchanger performs a preliminary action by pre-cooling the desiccant before it enters the absorber. This pre-cooling enhances the desiccant's effectiveness in the absorber, allowing the system to operate at lower desiccant flow rates and reduce the energy required by pumps
3Productivity
If existing liquid-desiccant air conditioners are used, then dehumidification is achieved, but air-side pressure drops increase, reducing system efficiency
Solution Approach 1:
The invention optimizes operational parameters including desiccant flow rate and temperature to maximize dehumidification efficiency at lower values. By pre-cooling the desiccant and operating at optimized flow rates, the system achieves effective dehumidification with reduced air-side pressure drops compared to existing systems
4Loss of energy
If thermal energy from refrigerant condenser is used to regenerate desiccant, then latent cooling efficiency is improved, but device complexity increases
Solution Approach 1:
The heat exchanger serves multiple functions: it pre-cools the desiccant before it enters the absorber and pre-heats the cooling air before it enters the regenerator. This multi-functionality allows the system to improve latent cooling efficiency while adding minimal complexity, as a single component performs multiple thermal management tasks
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 configuration enhances latent cooling efficiency by reducing desiccant flow rates, minimizing energy transfer, and allowing independent control of latent and sensible cooling, thereby improving overall air conditioning performance and reducing energy consumption and capital costs.
Implementation Method 1
Desiccants are materials with a high affinity for water vapor. They can be used to directly absorb water vapor from air without first cooling the air below its dewpoint temperature.
Implementation Method 2
After the desiccant absorbs water vapor it is heated so that the absorbed water vapor is released to an appropriate sink (e.g., the outdoor ambient). This release of water vapor regenerates the desiccant
Implementation Method 3
The thermal energy for regenerating the desiccant is supplied by the refrigerant condenser of a vapor-compression heat pump
Implementation Method 4
a refrigerant evaporator that cools the process air
Data Source
AI summary
A device for cooling and dehumidifying a first stream of air includes a first heat exchanger that cools the first stream of air from a first temperature to a lower second temperature, an absorber, a regenerator and one or more pumps and conduits. The device operates under conditions where liquid desiccant removes moisture from the first stream of air in the absorber and the second temperature of the first stream of air that leaves the first heat exchanger is lower than the temperature of the liquid desiccant supplied to the absorber.