Asymmetric evaporator

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Solution Overview

Problem

In falling film evaporators of HVAC systems, undesirable amounts of liquid refrigerant are entrained in the vapor, leading to negative impacts on compressor performance due to inefficient vapor direction and refrigerant distribution.

Innovation Solution

The design incorporates unequal gaps between wall members and tube sheets to bias the vapor flow, reducing the entrainment of liquid refrigerant by creating a longer path for vapor to reach the outlet, and optionally using asymmetric constructions to further direct vapor flow away from the suction line.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a sheath is used to direct vapor downward toward the refrigerant pool, then vapor direction is improved, but liquid refrigerant entrainment in the vapor increases

Engineering Contradiction:

Improvevapor directionVSAvoidliquid refrigerant entrainment

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent applies asymmetry by creating unequal gaps between the wall members and tube sheets. Specifically, one gap is larger than the other, which asymmetrically directs the vapor flow path. This asymmetric configuration allows vapor to be directed toward the outlet while the larger gap provides a longer path that reduces liquid refrigerant entrainment, resolving the contradiction between vapor direction control and liquid carryover prevention.

Inventive Principle:

Principle #4Asymmetry

2Productivity

If compressor guide vanes and system metering tools are used to control refrigerant circulation, then total rate of refrigerant circulation is controlled, but maintaining adequate refrigerant level becomes difficult

Engineering Contradiction:

Improverefrigerant circulation rateVSAvoidrefrigerant level maintenance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The evaporator design allows the system to self-regulate refrigerant distribution through its asymmetric geometry. The unequal gaps create natural flow patterns that promote even refrigerant distribution across the evaporator tubes without requiring complex external control mechanisms, enabling the system to maintain adequate refrigerant levels through its own structural characteristics rather than relying entirely on external metering tools.

Inventive Principle:

Principle #25Self-service

3Ease of operation

If vapor is forced downward through the sheath, then vapor flow direction is controlled, but the path length for vapor to reach the outlet is reduced

Engineering Contradiction:

Improvevapor flow directionVSAvoidvapor path length

Core Design Contradiction:

Ease of operationVSLength of moving object

Solution Approach 1:

The asymmetric gap configuration between wall members and tube sheets creates unequal flow paths for vapor. By making one gap larger than the other, the design extends the vapor travel distance through the larger gap while still maintaining directional control. This resolves the contradiction by using asymmetry to simultaneously achieve flow direction control and increased path length for liquid settlement.

Inventive Principle:

Principle #4Asymmetry

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 effectively decreases the amount of liquid refrigerant carried over to the compressor, enhancing compressor performance by minimizing liquid entrainment and improving vapor distribution.

Implementation Method 1

use an evaporator to facilitate a thermal energy exchange between a refrigerant in the evaporator and a medium flowing in a number of evaporator tubes positioned in the evaporator

Methodology Applied

Scientific EffectThermal energy exchange: Heat Exchanger

Implementation Method 2

A first gap between a first wall member lower edge and the plurality of tube sheets is greater than second gap between a second wall member lower edge and the plurality of tube sheets

Methodology Applied

Scientific EffectVapor flow biasing:

Data Source

PatentUS10429106B2Asymmetric evaporator

Publication Date: 2019.10.01 CARRIER CORP

AI summary

A falling film evaporator includes an evaporator housing and a plurality of evaporator tubes disposed in the evaporator housing and arranged into one or more tube bundles, through which a volume of thermal energy transfer medium is flowed. A plurality of tube sheets support the plurality of evaporator tubes. A first wall member and a second wall member extend vertically at opposite lateral sides of the plurality of evaporator tubes. The first wall member and the second wall member define an inner vapor passage therebetween, define a first outer vapor passage between the first wall member and the evaporator housing, and define a second outer vapor passage between the second wall member and the evaporator housing. A first gap between a first wall member lower edge and the plurality of tube sheets is greater than second gap between a second wall member lower edge and the plurality of tube sheets.