Evaporator Mixing Manifold for Uniform Two-Phase Refrigerant Flow
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Solution Overview
Problem
In multichannel heat exchangers, the separation of vapor and liquid refrigerant phases leads to inefficient heat transfer due to vapor-rich channels not absorbing heat effectively, reducing overall heat absorption and transfer efficiency.
Innovation Solution
A heat exchanger design incorporating a first manifold to mix liquid and vapor phases, directing the mixed flow through multichannel tubes, with configurations such as helical tapes, partitions with apertures, and baffles to promote phase mixing and ensure a homogeneous refrigerant distribution within the tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If refrigerant flows through multichannel tubes without phase mixing, then vapor-liquid separation occurs, but heat transfer efficiency deteriorates due to vapor-rich channels not absorbing heat effectively
Solution Approach 1:
A flow mixer is introduced as an intermediary device within the manifold to actively mix the vapor-liquid refrigerant mixture before it enters the multichannel tubes. This mediator prevents phase separation by creating turbulent flow and redistributing the phases uniformly across all channels, ensuring each tube receives a consistent liquid-vapor mixture for efficient heat transfer.
Solution Approach 2:
The flow mixer performs preliminary mixing action on the refrigerant phases before the mixture enters the heat transfer tubes. By pre-mixing the phases in the manifold, the system ensures uniform phase distribution is established beforehand, preventing separation from occurring during flow through the tubes and maintaining consistent heat absorption across all channels.
2Quantity of substance
If expansion device creates vapor during refrigerant expansion, then refrigerant volume increases, but liquid refrigerant ratio decreases leading to reduced heat absorption capacity
Solution Approach 1:
The flow mixer acts as an intermediary that redistributes the vapor and liquid phases created during expansion. It uses the kinetic energy and pressure differential to force liquid refrigerant into channels that might otherwise receive excessive vapor, ensuring optimal liquid distribution for heat absorption while accommodating the increased refrigerant volume from expansion.
Solution Approach 2:
The flow mixer changes the flow parameters (velocity, pressure distribution, flow pattern) of the refrigerant mixture. By creating turbulent flow and altering the distribution parameters, it ensures liquid refrigerant is delivered to channels at optimal rates, maximizing heat absorption capacity despite the presence of vapor from expansion.
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
Enhances heat transfer efficiency by maintaining a higher ratio of liquid refrigerant in the channels, preventing vapor separation and ensuring consistent heat absorption across all tubes, thereby improving the overall performance of HVAC&R systems.
Implementation Method 1
a flow mixer included in the first manifold to promote mixing of liquid and vapor phases within the multichannel tubes
Implementation Method 2
the refrigerant may enter an evaporator heat exchanger as a liquid and exit as a vapor... while some energy is transferred to and from the refrigerant by changes in the temperature of the fluid (i.e., sensible heat), more energy is exchanged by phase changes (i.e., latent heat)
Implementation Method 3
the liquid refrigerant flowing through the heat exchanger absorbs heat from the air causing the liquid refrigerant to change to a vapor
Data Source
AI summary
Heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems and heat exchangers are provided which include manifold configurations designed to promote mixing of vapor phase and liquid phase refrigerant. The manifolds contain flow mixers such as a helical tape, sectioned volumes, and partitions containing apertures. The flow mixers direct the flow of refrigerant within the manifold to promote a more homogenous distribution of fluid within the multichannel tubes.