HVAC Heat Exchanger Control for Decoupled Humidity and Defrost-Free Cooling

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Solution Overview

Problem

Current HVAC systems face challenges in independently controlling temperature and relative humidity, leading to issues like frost formation and increased energy consumption, particularly in dry environments where electrostatic discharge is common, and in refrigeration systems where defrosting disrupts chilling cycles.

Innovation Solution

Implementing a thermodynamically decoupled control system that varies air velocity through a heat exchanger, utilizing nanostructured coatings to promote jumping droplet condensation, which prevents frost formation and increases condensate rejection, thereby allowing independent control of temperature and humidity, and using droplet ejection coatings to suppress frost formation below freezing points.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If thermostatic temperature control is used in HVAC systems, then temperature setpoint is maintained, but relative humidity becomes coupled and cannot be independently controlled

Engineering Contradiction:

Improvetemperature setpointVSAvoidindependent humidity control

Core Design Contradiction:

TemperatureVSAdaptability or versatility

Solution Approach 1:

The system segments temperature and humidity control into separate independent control loops. Temperature is controlled by traditional thermostatic means while humidity is controlled by a separate humidifier system with its own sensor and control algorithm, allowing both parameters to be maintained at their respective setpoints simultaneously without thermodynamic coupling.

Inventive Principle:

Principle #1Segmentation

2Temperature

If cooling is performed in dry environments, then temperature is reduced, but moisture is removed and air becomes too dry causing discomfort and electrostatic discharge

Engineering Contradiction:

Improvecooling temperatureVSAvoidelectrostatic discharge prevention

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The system uses a humidifier sensor to continuously monitor relative humidity levels and provides feedback to the control system. When humidity drops below the setpoint during cooling operations, the humidifier is activated to add moisture back into the air, maintaining humidity within the comfortable and safe range even while temperature is reduced.

Inventive Principle:

Principle #23Feedback

3Reliability

If refrigeration systems defrost evaporator coils periodically, then frost is removed, but energy consumption increases and chilling cycles are interrupted

Engineering Contradiction:

Improvefrost removalVSAvoidchilling throughput

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system uses the cold evaporator coil surface, which would normally cause frost formation, as a beneficial condensation surface. By controlling the microenvironment and using hydrophobic coatings, condensed moisture is directed away from the coil surface before it can freeze, converting the potentially harmful frost-forming condition into a beneficial condensation-and-drainage process that prevents frost accumulation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Ease of manufacture

If hydrophobic coatings are used on heat exchangers, then water beads and is dragged into collection pan, but some droplets become entrained and revaporize causing temperature decrease and humidity increase

Engineering Contradiction:

Improvecondensate drainageVSAvoidair stream temperature

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The system applies hydrophobic coatings to specific local areas of the heat exchanger where condensation occurs, while maintaining different surface properties in other areas. This localized treatment directs condensate formation and drainage to specific collection points, minimizing the opportunity for droplet entrainment and revaporization while maintaining effective condensate removal.

Inventive Principle:

Principle #3Local quality

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 approach reduces frost formation, increases the throughput of chilled products, and enhances the efficiency of HVAC and refrigeration systems by minimizing energy usage and eliminating the need for frequent defrosting, resulting in improved system performance and comfort settings.

Implementation Method 1

jumping droplet condensation on at least one surface of a heat exchanger through which the air travels

Methodology Applied

Scientific EffectJumping droplet condensation: Leidenfrost Effect

Implementation Method 2

The air is cooled adiabatically along a line of constant enthalpy

Methodology Applied

Scientific EffectAdiabatic cooling: Adiabatic Cooling

Implementation Method 3

HVAC-R systems coated with hydrophobic materials cause the water to bead on the surface

Methodology Applied

Scientific EffectHydrophobic effect: Hydrophobe

Data Source

PatentUS11473807B2Temperature and relative humidity controller

Publication Date: 2022.10.18 NELUMBO INC

AI summary

Control systems are provided that provide thermodynamically decoupled control of temperature and relative humidity and/or reduce or prevent frost formation or remove previously-formed frost. The control systems herein may be included as a component of a heating, ventilation, air conditioning, and refrigeration system that includes a heat exchanger.