Multichannel Evaporator Manifold for Refrigerant Phase Mixing
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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 featuring 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.
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 a homogeneous distribution of liquid and vapor phases across all channels, ensuring that each channel receives a balanced mixture rather than allowing vapor to accumulate in certain channels and liquid in others.
Solution Approach 2:
The flow mixer changes the flow parameters of the refrigerant by creating turbulence and enhancing mixing. This alters the velocity distribution and phase distribution of the refrigerant, transforming it from a separated state (vapor at top, liquid at bottom) into a well-mixed state that maintains homogeneous phase distribution throughout the multichannel tubes, thereby improving heat transfer efficiency.
2Temperature
If expansion device increases refrigerant volume, then temperature and pressure are lowered, but vapor formation occurs during expansion reducing liquid refrigerant quality
Solution Approach 1:
The flow mixer performs preliminary mixing action immediately after the expansion device, before the refrigerant enters the evaporator tubes. By pre-mixing the vapor-liquid mixture right after expansion, the system compensates for the vapor formation that occurred during expansion, ensuring that the refrigerant entering the evaporator has optimal liquid quality for efficient heat absorption.
3Productivity
If vapor refrigerant separates from liquid refrigerant, then vapor accumulates in certain channels, but heat absorption capacity is reduced in vapor-rich channels
Solution Approach 1:
The flow mixer acts as an intermediary that prevents vapor accumulation by continuously mixing the vapor-liquid refrigerant mixture. This ensures uniform phase distribution across all channels, preventing any single channel from becoming vapor-rich and losing its heat absorption capacity.
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 flow channels, preventing vapor separation and ensuring that all channels absorb heat, thereby maximizing heat absorption and transfer.
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 liquid refrigerant flowing through the heat exchanger absorbs heat from the air causing the liquid refrigerant to change to a vapor
Implementation Method 3
Heat exchangers transfer heat by circulating a refrigerant through a cycle of evaporation and condensation
Implementation Method 4
The expansion device lowers the temperature and pressure of the refrigerant by increasing its volume
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.