Sequential Heat Pump Cycle Using Thermal Storage for Higher Heating COP
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Solution Overview
Problem
Conventional vapor compression cycle systems face inefficiencies and environmental concerns due to the use of HFC refrigerants, particularly R410A, which have high global warming potential, and CO2 (R744) systems that struggle with low COP in heating modes, leading to increased CO2 emissions from energy sources.
Innovation Solution
A dual-function thermal energy reservoir system that acts as both an evaporator and gas cooler/condenser, utilizing CO2 as the working fluid, with a two-tank temperature system for preheating sanitary water and regulating energy flow based on recurring temperatures and heat demand, allowing for optimized heat production and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If CO2 (R744) is used as refrigerant to reduce environmental impact, then greenhouse gas emissions from refrigerant leakage are reduced, but the COP in heating mode deteriorates due to low critical point
Solution Approach 1:
The system preheats water in the thermal energy reservoir during daytime when ambient temperature is high, storing thermal energy for nighttime use. This preliminary action allows the heat pump to operate more efficiently during nighttime heating by utilizing the pre-stored thermal energy, thereby improving overall COP while maintaining environmental benefits of CO2 refrigerant
Solution Approach 2:
The system operates in periodic cycles between daytime charging mode (storing thermal energy in the reservoir) and nighttime discharging mode (utilizing stored energy for heating). This periodic operation optimizes the heat pump's performance by matching operational demands with favorable ambient conditions, improving COP while using CO2 refrigerant
2Device complexity
If ambient air is used as heat source for evaporation, then system simplicity is maintained, but de-icing energy consumption increases during low temperature operation
Solution Approach 1:
The thermal energy reservoir is preheated during daytime to store thermal energy, which is then used during nighttime to prevent ice formation on the evaporator. This preliminary heating action eliminates the need for energy-consuming de-icing operations during low temperature nighttime operation, reducing energy loss while maintaining system simplicity
Solution Approach 2:
The thermal energy reservoir acts as an intermediary thermal buffer between the ambient air and the evaporator. It absorbs excess heat during daytime and releases it during nighttime to prevent evaporator freezing, thereby reducing de-icing energy consumption without adding complex de-icing equipment
3Loss of energy
If thermal energy reservoir is used for preheating water, then heat transfer efficiency is improved, but system complexity increases with additional components
Solution Approach 1:
The thermal energy reservoir serves multiple functions: it acts as a heat source for the evaporator during nighttime, a heat sink for condensing heat during daytime, and a preheating tank for domestic hot water. This multi-functionality improves heat transfer efficiency by maximizing thermal energy utilization while minimizing additional system complexity
Solution Approach 2:
The heat pump system operates in multiple modes using the same components: heating mode (nighttime), cooling mode (daytime), and hot water production mode. This operational versatility improves overall system efficiency by optimizing heat transfer in different conditions without requiring separate dedicated systems
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 enhances the efficiency of the vapor compression cycle by 12.5% through improved heat transfer, reduces noise and de-icing energy consumption, increases compressor longevity, and allows for more effective harnessing of thermal energy from solar collectors, while minimizing greenhouse gas emissions.
Implementation Method 1
The pressure and temperature of the refrigerant is increased by the compressor 1
Implementation Method 2
the refrigerant rejects heat in the second heat exchanger 2r and 2p
Implementation Method 3
the refrigerant is cooled and/or condensed, giving off heat
Implementation Method 4
The high-pressure liquid is then throttled to the evaporator pressure by means of the pressure reduction device 3
Implementation Method 5
In the evaporator 4, the refrigerant boils and absorbs heat from its surroundings
Implementation Method 6
the refrigerant is cooled and/or condensed, giving off heat
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A system for providing a vapour compression cycle, comprises a compressor (1 ). A first heat exchanger (2) is arranged downstream of the compressor (1 ), and a first pressure reduction device (5) lies downstream of the first heat exchanger (2). A second heat exchanger (6) with a heat storage device (7) lies downstream of the first pressure reduction device (5), and a second pressure reduction device (3) is provided downstream of the second heat exchanger 6. A third heat exchanger (4) lies downstream of the second pressure reduction device (3) connected back to the compressor 1. A bypass line with a shutoff valve (8), bypasses the third heat exchanger (4), connected at a first end between the second heat exchanger (6) and the second pressure reduction device (3) and at a second end, between the third heat exchanger (4) and the compressor (1 ). At least one control unit controls at least the shutoff valve (8) and the second pressure reduction device (3) and the first pressure reduction device (5).