Multiple-Mode Hybrid Heat Exchanger for Freeze-Resistant Cooling
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Solution Overview
Problem
Conventional heat exchangers face inefficiencies in varying temperature conditions, such as freezing issues and increased costs due to tightly packed tubes and fins, which affect performance and operational costs.
Innovation Solution
A multiple mode hybrid heat exchanger that can operate in evaporative, dry, and adiabatic modes, utilizing a frame assembly with indirect and direct heat exchange sections, adjustable dampers, and a spray system to optimize airflow and water flow based on environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If water is sprayed on heat exchange conduits to enhance heat transfer, then heat transfer efficiency is improved, but freezing occurs in cold conditions
Solution Approach 1:
The system dynamically switches between different operational modes (evaporative, dry, adiabatic) based on ambient temperature conditions. The spray system is activated only when temperature is above freezing, while the dry mode is engaged when temperature drops below freezing, preventing freezing while maintaining heat transfer efficiency across varying conditions
2Productivity
If tubes are tightly packed to increase heat transfer surface area, then heat transfer efficiency is improved, but fan horsepower and unit cost increase
Solution Approach 1:
The heat exchanger is divided into multiple tube passes with strategic spacing. Instead of uniformly packing all tubes tightly, the design segments the tube arrangement to optimize airflow patterns, reducing the total fan horsepower required while maintaining effective heat transfer surface area through the multi-pass configuration
3Productivity
If fins are added between tubes to increase heat exchange surface area, then heat transfer efficiency is improved, but fouling and particle build up increase
Solution Approach 1:
The design extracts or removes the fin elements from the heat exchanger configuration. Instead of adding fins between tubes, the system relies on the tube surfaces themselves and the evaporative cooling effect, eliminating the fins that would otherwise accumulate fouling and particles while maintaining adequate heat transfer efficiency
4Device complexity
If the heat exchanger operates in a single mode, then the design is simple, but it fails to operate well at different temperature conditions
Solution Approach 1:
The heat exchanger is designed with multi-functionality to operate effectively across different temperature conditions. It incorporates a spray system for evaporative cooling, dry mode operation, and adiabatic mode, allowing it to adapt to varying ambient temperatures and maintain optimal performance across diverse environmental conditions
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 flexibility and efficiency across varying temperatures without increasing unit size or cost, preventing freezing, and reducing fouling susceptibility.
Implementation Method 1
Heat from the fluid or gas passing through the coil assembly tubes is transferred through the tube walls to the water sprayed over the tubes
Implementation Method 2
As the flowing air contacts the spray water on the tubes, partial evaporation of some of the spray water occurs along with a transfer of heat from the spray water to the air
Implementation Method 3
A fan is arranged to blow air into the air passage near the bottom thereof and up between the tubes in a counter flow relationship to the downwardly flowing spray water
Data Source
AI summary
A multiple mode hybrid heat exchanger apparatus is disclosed. The heat exchange apparatus includes a frame assembly having a first end wall, a second end wall, a first side wall, a second side wall, an indirect heat exchange section, a spray system, an intermediate distribution basin, and a direct heat exchange section. A vertical passage is defined by the frame assembly and the direct heat exchange section. A lower air inlet is defined by a plurality of openings in the direct heat exchange section, and the lower air inlet is configured to provide an inlet for air into the vertical passage. The apparatus further includes a cold water collection basin and a fan to induce an airflow through the lower air inlet. The multiple mode hybrid heat exchanger apparatus is selectably configured to operate in an evaporative mode, a dry mode, and an adiabatic mode.