Variable refrigerant flow system with reheating of dehumidified air
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Solution Overview
Problem
Variable refrigerant flow (VRF) systems face challenges in controlling the temperature of reheated air, leading to overcooling or overheating in spaces, due to fixed refrigerant flow ratios and varying ambient conditions, which affects comfort levels.
Innovation Solution
The system controls refrigerant flow to a reheater by directing a portion of hot refrigerant from the compressor to the reheater during heating mode and to the outdoor heat exchanger during cooling mode, using a solenoid valve to regulate the refrigerant flow ratio, allowing for precise temperature control of reheated air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the indoor heat exchanger cools air to condense water vapor and reduce humidity level, then the humidity control is improved, but the air temperature becomes too low causing overcooling of the space
Solution Approach 1:
The patent segments the refrigerant flow into two separate paths using a first valve and second valve: one path through the indoor heat exchanger for dehumidification, and another path through the reheater for temperature control. This allows independent control of humidity removal and temperature adjustment, resolving the contradiction between removing moisture and maintaining comfortable air temperature.
Solution Approach 2:
The reheater acts as an intermediary component between the indoor heat exchanger and the space. It receives overcooled air and reheats it using a second refrigerant flow before supplying air to the space. This intermediary step prevents the direct delivery of overcooled air while maintaining the dehumidification effect.
2Temperature
If a reheater is used to heat overcooled air, then the air temperature is improved, but it becomes difficult to control the amount of reheating causing supply air to be too hot or too cold
Solution Approach 1:
The patent employs dynamic control of refrigerant flow distribution to the reheater and indoor heat exchanger through electronically controlled valves. The system can adjust the proportion of refrigerant flow to each component in real-time based on temperature sensors and control logic, enabling precise control of supply air temperature and resolving the difficulty of controlling reheating amount.
Solution Approach 2:
The system changes the operating parameters of the refrigerant flow distribution by adjusting valve positions and refrigerant flow rates. By dynamically modifying these parameters based on feedback from temperature sensors, the system achieves precise control over the reheating process and maintains supply air temperature within the desired range.
3Device complexity
If the same refrigerant flow passes through both the indoor heat exchanger and reheater in series, then the system structure is simplified, but the net effect of cooling and heating capacities causes supply air temperature offset from setpoint
Solution Approach 1:
The patent divides the refrigerant flow into parallel segments rather than using a single series flow. The first valve and second valve create separate refrigerant paths: one through the indoor heat exchanger and another through the reheater. This segmentation allows independent control of cooling and heating capacities, eliminating the temperature offset problem while maintaining reasonable system complexity.
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 enables controlled reheating of overcooled air, improving comfort levels by ensuring the air temperature is neither too cold nor too hot, thus enhancing the overall thermal comfort in spaces.
Implementation Method 1
the first heat exchanger removes heat from a first portion of the refrigerant from the compressor
Implementation Method 2
the second heat exchanger uses the first portion of the refrigerant from the first heat exchanger and the second portion of the refrigerant from the reheater to cool air proximate the second heat exchanger
Implementation Method 3
the reheater uses the second portion of the refrigerant from the compressor to heat the air moved by the blower
Data Source
AI summary
An apparatus includes a compressor, a first heat exchanger, a reheater, a first valve, a second heat exchanger, and a blower. The compressor compresses a refrigerant. The blower moves air proximate the second heat exchanger to the reheater. During a first mode of operation: the first heat exchanger removes heat from a first portion of the refrigerant from the compressor, the first valve opens such that a second portion of the refrigerant from the compressor flows to the reheater, the second heat exchanger uses the first portion of the refrigerant from the first heat exchanger and the second portion of the refrigerant from the reheater to cool air proximate the second heat exchanger, and the reheater uses the second portion of the refrigerant from the compressor to heat the air moved by the blower.