Return Waterbox Insert for Heat Exchanger Bypass Reduction
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Solution Overview
Problem
Shell-and-tube heat exchangers in chiller systems face inefficiencies due to water by-pass, where upper section heat exchanger tubes have reduced refrigerant wetting, leading to elevated return water temperatures and increased compressor lift, especially at partial load conditions, which reduces overall chiller efficiency.
Innovation Solution
A return waterbox with an insert that divides the flow into compartments with diagonal flow paths, redirecting water from upper section tubes to lower section tubes in a multi-pass design, enhancing heat exchange uniformity and reducing by-pass, potentially using less expensive materials like steel for upper section tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional return waterbox is used in a multi-pass heat exchanger, then the structure is simple, but water by-pass occurs in the upper section tubes leading to reduced heat exchange efficiency
Solution Approach 1:
The return waterbox is divided into multiple compartments (first compartment, second compartment, third compartment) using partitions. This segmentation directs water flows through different paths, ensuring that water from upper section tubes is redirected to lower section tubes and vice versa, eliminating water by-pass and improving heat exchange efficiency.
Solution Approach 2:
Partitions act as intermediary structures within the return waterbox to control and redirect fluid flow. The partitions create designated flow paths that mediate between the incoming water from tubes and the outgoing water to tubes, ensuring proper flow distribution and preventing by-pass.
2Temperature
If upper section tubes are used without flow redirection, then the structure is simple, but refrigerant wetting is reduced leading to elevated return water temperatures
Solution Approach 1:
The return waterbox inverts the normal flow pattern by redirecting water from upper section tubes to lower section tubes and from lower section tubes to upper section tubes. This inversion ensures that all tubes receive adequate refrigerant wetting, maintaining uniform heat exchange and preventing elevated return water temperatures.
Solution Approach 2:
Different compartments within the return waterbox provide different flow paths tailored to specific tube sections. The first compartment handles flow from upper tubes, the second compartment handles flow from lower tubes, ensuring that each section receives appropriate flow management for optimal heat exchange.
3Temperature
If compressor lift is increased to compensate for by-pass, then the temperature control is improved, but energy consumption increases
Solution Approach 1:
The return waterbox structure itself provides the temperature control function by ensuring uniform heat exchange across all tubes. This self-service approach eliminates the need for additional compressor work to compensate for by-pass, maintaining temperature control while minimizing energy consumption.
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 improves heat exchange efficiency by ensuring uniform temperature distribution and reducing the need for increased compressor lift, while also lowering the cost of heat exchanger materials by using less efficient materials in areas prone to by-pass.
Implementation Method 1
The return waterbox may include a structure that is configured to divide the return waterbox into at least two compartments and direct a fluid flow(s) (e.g. water flows) in the compartments
Implementation Method 2
The heat exchanger tubes define a tube side configured to carry a first fluid (e.g. water); and the shell defines a shell side configured to carry a second fluid (e.g. refrigerant). The tube side and the shell side can form a heat exchange relationship to transfer heat between the first fluid and the second fluid
Data Source
AI summary
A return waterbox for a heat exchanger, such as a shell-and-tube heat exchanger, is provided. The return waterbox may include an insert configured to direct a fluid flow(s) in the return waterbox. In some embodiments, such as in a two-pass heat exchanger, the insert can be configured to receive water from one portion of the heat exchanger tubes in the first pass and redirect the received water to another portion of the heat exchanger tubes in the second pass.