Air source CO<sub>2 </sub>heat pump system for preventing evaporator from frosting by using heat of heat regenerator

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Solution Overview

Problem

Air source CO2 heat pumps face performance degradation and frosting issues under variable load conditions, leading to increased energy consumption and reduced heating capacity due to frost accumulation on the evaporator surface.

Innovation Solution

An air source CO2 heat pump system incorporating a regenerative heat exchange tank with a phase change material and a tube-in-tube internal heat exchanger, which utilizes regenerative heat to reduce evaporator frosting by lowering the temperature at the expansion valve inlet and providing heat for defrosting, thereby improving system performance and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If CO2 heat pump operates under variable load conditions, then heating capacity adapts to demand changes, but evaporator frosting occurs and system performance degrades

Engineering Contradiction:

Improveheating capacity adaptationVSAvoidsystem performance stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The regenerative heat exchange tank pre-cools the CO2 refrigerant before it enters the evaporator by utilizing stored heat from the gas cooler. This preliminary heat exchange action prevents the evaporator surface temperature from dropping too low, thereby preventing frosting before it occurs while maintaining variable load operation capability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The regenerative heat exchange tank acts as an intermediary component between the gas cooler and the evaporator. It stores thermal energy from the high-temperature CO2 in the gas cooler and releases it to pre-cool the incoming CO2, mediating the temperature differences that would otherwise cause evaporator frosting under variable load conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If CO2 temperature at expansion valve inlet is reduced to improve heating efficiency, then COP increases, but evaporator frosting risk increases

Engineering Contradiction:

Improveheating efficiencyVSAvoidevaporator frosting

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The regenerative heat exchange tank utilizes the phase change characteristics of CO2 refrigerant. By controlling the heat exchange process in the tank, the CO2 undergoes controlled temperature and phase transitions that allow efficient heat transfer while preventing the evaporator surface temperature from reaching the frosting point

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The system performs preliminary heat exchange in the regenerative tank before the CO2 reaches the expansion valve and evaporator. This preliminary action adjusts the CO2 temperature to an optimal range that maintains high heating efficiency while preventing excessive cold that would cause frosting

Inventive Principle:

Principle #10Preliminary action

3Productivity

If heat is released from CO2 in gas cooler, then heating capacity increases, but available heat for defrosting is insufficient

Engineering Contradiction:

Improveheating capacityVSAvoidheat utilization for defrosting

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The regenerative heat exchange tank continuously stores thermal energy from the gas cooler during system operation. This continuous heat accumulation ensures that sufficient heat is always available for defrosting operations, maintaining both high heating capacity and effective heat utilization without energy loss

Inventive Principle:

Principle #20Continuity of useful action

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

The system effectively prevents evaporator frosting, enhances performance under variable loads, and achieves stable and efficient heating by using regenerative heat for defrosting and heat storage, reducing throttling loss and power consumption.

Implementation Method 1

a tank body of the regenerative heat exchange tank is filled with a phase change material

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 2

a tube-in-tube internal heat exchanger and a cooling liquid heat exchange tube of single-spiral finned tube type are provided within the tank body

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 3

a cooling liquid heat exchange tube of single-spiral finned tube type

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

a cooling liquid heat exchange tube of single-spiral finned tube type are arranged at intervals in a spiral mode

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS11674724B2Air source CO<sub>2 </sub>heat pump system for preventing evaporator from frosting by using heat of heat regenerator

Publication Date: 2023.06.13 TSINGHUA UNIVERSITY

AI summary

The present disclosure relates to the technical field of heat pumps, in particular to an air source CO2 heat pump system for preventing an evaporator from frosting by using heat of a heat regenerator. The air source CO2 heat pump system mainly includes an air source heat pump system, a regenerative heat exchange tank and a cooling pump. Through the regenerative heat exchange tank, on the one hand, the temperature drop of regenerative heat of the system is further increased and throttling loss is reduced; on the other hand, the heat generated by the regenerative temperature drop is configured for heat storage used for defrosting, and configured for overheating temperature rise.