Heat pump system and method for air conditioning
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Solution Overview
Problem
Conventional heat pump systems face inefficiencies in temperature and humidity control, particularly in managing the circulation and interaction of refrigerant, brine, and ambient air, which affects the balance of sensible and latent loads in air conditioning systems.
Innovation Solution
A heat pump system utilizing two units with direct contact air/brine heat exchangers and brine/refrigerant heat exchangers, where porous pads facilitate intimate air-brine contact, and a method that supplies liquid brine and ambient air in a transverse direction through the heat exchangers to manage temperature and humidity, using hygroscopic brines like LiBr and MgCl2 to prevent precipitation and ice formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional refrigerant circulation systems are used with finned pipes, then heating and cooling functions are provided, but temperature and humidity control efficiency is insufficient and the balance of sensible and latent loads is poor
Solution Approach 1:
The system divides the air conditioning function into two separate units: one for sensible cooling (removing heat) and another for latent cooling (removing moisture). Each unit handles a specific aspect of the thermal load, improving overall efficiency by addressing sensible and latent heat separately rather than through a single conventional refrigerant cycle.
Solution Approach 2:
Brine is introduced as an intermediary substance between the refrigerant system and the ambient air. The refrigerant cools the brine, and the cooled brine then contacts ambient air in the heat exchanger pads, enabling efficient heat and moisture transfer. This intermediary approach allows independent optimization of refrigerant cycle and air treatment processes.
2Productivity
If direct contact air/brine heat exchangers with porous pads are used, then intimate air-brine contact is achieved for improved heat and mass transfer, but device complexity increases
Solution Approach 1:
Porous pads are used as the heat exchanger medium, allowing simultaneous passage of air and brine through their interconnected void spaces. This creates extensive contact surface area between the two fluids, dramatically enhancing heat and mass transfer efficiency while maintaining a relatively simple overall structure.
Solution Approach 2:
The porous pads are designed to be naturally wetted by brine flowing through them, eliminating the need for additional spraying mechanisms or complex distribution systems. The brine circulation system automatically maintains the pads in a wet state, and the pads' structure self-regulates the contact between air and brine.
3Reliability
If hygroscopic brines like LiBr and MgCl2 are used to prevent precipitation and ice formation, then reliable operation across working temperature range is achieved, but loss of substance occurs through potential salt precipitation
Solution Approach 1:
The system carefully controls the concentration and composition parameters of the brine solution to optimize its hygroscopic properties. By adjusting these parameters, the brine maintains effectiveness across the full working temperature range without reaching saturation points that would cause salt precipitation or ice formation, ensuring reliable operation.
Solution Approach 2:
The naturally hygroscopic property of brines, which could potentially lead to salt precipitation and material loss, is converted into a benefit by selecting concentrations that maximize moisture absorption while remaining below saturation limits. This transforms what could be a harmful precipitation tendency into a useful moisture-capturing mechanism.
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
The system effectively reduces air temperature and humidity, balancing sensible and latent loads, enhancing cooling and heating capacities while maintaining efficient operation and preventing salt or ice precipitation within the working temperature range.
Implementation Method 1
direct contact air/brine heat exchanger pads that are wetted by brine flowing through the pads, and are permeable to air that is drawn or forced through the pads, to provide intimate contact between the brine and the air
Implementation Method 2
the brine flows downwardly through the heat exchanger pad... ambient air into the heat exchanger pad in a direction transverse to the flow of brine through the pad
Implementation Method 3
two brine/refrigerant heat exchangers are coupled to the brine reservoirs for receiving brine from the reservoirs
Implementation Method 4
Hygroscopic brine such as LiBr, MgCl2, CaCl2 and mixtures thereof, can be advantageously used. The concentrations of these brines are such that no precipitation of salts or ice occurs throughout the working temperature range of the heat pump
Data Source
AI summary
A heat pump system comprises two units in fluid communication with each other, with each unit including a housing containing an air/brine heat exchanger that includes a direct contact air/brine heat exchanger pad. A brine inlet in the housing supplies liquid brine to the upper end of the air/brine heat exchanger so that the brine flows downwardly through the heat exchanger pad. An air inlet in the housing directs ambient air into the heat exchanger pad in a direction transverse to the flow of brine through the pad, and an air outlet discharges the air from the housing. A brine reservoir receives brine passed through the air/brine heat exchanger. A pair of brine/refrigerant heat exchangers is coupled to the brine reservoirs, for receiving brine from the reservoirs, and coupled to the brine inlets of different ones of the housings, and a refrigerant supply supplies refrigerant to the brine/refrigerant heat exchangers.