HRV/ERV Heat Exchanger Defrost Using Recirculated Supply Air

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Solution Overview

Problem

Existing HVAC systems face challenges in efficiently defrosting heat exchanger cores during cold weather conditions, leading to restricted airflow and potential system failure.

Innovation Solution

The apparatus includes a damper mechanism that pivots to redirect supply air through a heat exchanger core, allowing it to defrost by recirculating warm air, and a control module that switches between normal and defrost modes based on temperature thresholds to prevent frost buildup.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the heat exchanger core operates in cold weather conditions, then heat exchange function is maintained, but frost buildup occurs leading to airflow restriction and potential system failure

Engineering Contradiction:

Improvesystem operation continuityVSAvoidfrost buildup on heat exchanger core

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control module monitors temperature conditions and initiates defrost mode before severe frost buildup occurs. When the temperature threshold is met, the damper proactively redirects supply air through the heat exchanger core to prevent frost accumulation, maintaining system reliability before the problem escalates

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system converts the potentially harmful cold supply air into a beneficial defrosting medium by redirecting it through the heat exchanger core. The cold supply air absorbs heat from the frosted surfaces, melting the frost and clearing the airflow paths, thus turning a harmful condition into a solution

Inventive Principle:

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

2Reliability

If a defrost system is added to the HVAC apparatus, then frost buildup is prevented, but device complexity increases

Engineering Contradiction:

Improveheat exchanger core defrosting capabilityVSAvoiddefrost system components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The damper mechanism serves multiple functions: it controls air flow distribution during normal operation and redirects supply air for defrosting when needed. The control module integrates temperature monitoring and mode switching, making the same components serve both operational and defrosting purposes, thereby avoiding additional dedicated defrost components

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The HVAC system uses its own supply air to defrost the heat exchanger core, eliminating the need for external heating elements or separate defrosting systems. The system's operational byproduct (supply air) is repurposed to solve the frost problem, reducing the need for additional complex defrosting infrastructure

Inventive Principle:

Principle #25Self-service

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 solution effectively defrosts the heat exchanger core, ensuring continuous operation by melting frost and maintaining optimal temperatures, thereby preventing airflow restrictions and system failures.

Implementation Method 1

a heat exchanger core arranged in the housing and comprising a first side and a second side segregated from the first side; an exhaust air chamber arranged between the exhaust air inlet and the first side of the heat exchanger core; an outside air chamber arranged between the outside air inlet and the second side of the heat exchanger core

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

so as to exchange heat between the exhaust air flowing through the first side of the heat exchanger core and the outside air

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

guiding outside air to flow to a second side of the heat exchanger core, so as to exchange heat between the exhaust air and the outside air

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 4

at least a portion of supply air is guided to flow from the supply air chamber through the outside air chamber to the second side of the heat exchanger core so as to defrost the heat exchanger core

Methodology Applied

Scientific EffectThermal melting: Melting

Implementation Method 5

effectively defrosts the heat exchanger core, ensuring continuous operation by melting frost and maintaining optimal temperatures

Methodology Applied

Scientific EffectThermal energy transfer: Heating

Data Source

PatentUS8939826B2HVAC apparatus with HRV/ERV unit and vertical fan coil unit

Publication Date: 2015.01.27 UNILUX VFC CORP

AI summary

An apparatus for heating, ventilation and/or air conditioning of an interior space includes a heat exchanger core and a heating/cooling device in fluid connection with the heat exchanger core. A recirculation port is arranged between a supply air chamber and an outside air chamber. A damper is adapted to move between a first position in which the damper blocks the recirculation port and a second position in which the recirculation port is unblocked. When the damper is in the second position, at least a portion of supply air is guided to flow from the supply air chamber through the outside air chamber to the heat exchanger core so as to defrost the heat exchanger core.