Cascade HVAC and Hot-Water Cycle With Bypass Startup Heating
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Solution Overview
Problem
Existing air-conditioning hot-water supply complex systems struggle to simultaneously provide a cooling load, a heating load, and a high-temperature hot-water supply load efficiently, as they often require continuous compressor operation and are not easily adaptable to installed air conditioners, leading to inefficiencies and instability in heat source provision throughout the year.
Innovation Solution
The system incorporates a cascade-connected air-conditioning and hot-water supply refrigeration cycle with a refrigerant-refrigerant heat exchanger and a heat medium-refrigerant heat exchanger, allowing for simultaneous or selective operation of air-cooling, air-heating, and hot-water supply operations, and includes a bypass pipe to enhance startup efficiency by rapidly increasing the temperature of the heat medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage refrigeration cycle is used to simultaneously provide cooling, heating, and hot-water supply, then the system structure is simple, but the system cannot cover high-temperature hot water supply load during cooling operation and cannot stably supply heating energy throughout the year
Solution Approach 1:
The refrigeration cycle is divided into two independent stages: a first refrigeration cycle for cooling and air conditioning, and a second refrigeration cycle for hot water supply. Each cycle operates independently with its own compressor and refrigerant circuit, allowing the system to simultaneously provide both cooling and high-temperature hot water supply without compromising either function.
Solution Approach 2:
The second refrigeration cycle is nested within the first refrigeration cycle structure. The second cycle's evaporator is integrated into the first cycle's refrigerant circuit, allowing heat exchange between the two cycles. This nested configuration enables the system to share common components like the outdoor heat exchanger while maintaining independent operation of each cycle.
2Adaptability or versatility
If a two-stage refrigeration cycle is used to simultaneously provide cooling, heating, and hot-water supply, then the system can cover high-temperature hot water supply load, but the refrigerant circuits for air conditioning and hot water supply are treated differently making it not easy to apply to installed air conditioners
Solution Approach 1:
The outdoor heat exchanger serves multiple functions: it acts as a condenser for the first refrigeration cycle during cooling operation, an evaporator for the first cycle during heating operation, and an evaporator for the second refrigeration cycle during hot water supply operation. This multi-functional design allows the system to be applied to installed air conditioners while providing high-temperature hot water supply capability.
Solution Approach 2:
The two refrigeration cycles are merged through shared components including the outdoor heat exchanger, refrigerant pipes, and control systems. The second cycle's evaporator is integrated into the first cycle's refrigerant circuit, creating a unified system structure that reduces complexity compared to completely separate circuits.
3Reliability
If the compressor continues working until the heat source is heated in a single-stage system, then the system can ensure heat supply, but the system is inefficient in operation
Solution Approach 1:
The second refrigeration cycle pre-heats the heat source water in the storage tank before the first cycle's compressor needs to operate for heating. The second cycle's compressor runs independently to raise the water temperature, so when heating is required, the heat source is already warmed, allowing the first cycle's compressor to start immediately without waiting for heat source heating, thus improving energy efficiency.
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 configuration enables efficient and stable operation by allowing simultaneous or selective loading of cooling, heating, and hot-water supply without complex circuitry, improving startup efficiency and maintaining a stable heat source throughout the year.
Implementation Method 1
the air-conditioning refrigeration cycle and the hot-water supply refrigeration cycle are cascade-connected so as to perform heat exchange between the air-conditioning refrigerant and the hot-water supply refrigerant in the refrigerant-refrigerant heat exchanger
Implementation Method 2
perform heat exchange between the air-conditioning refrigerant and the hot-water supply refrigerant in the refrigerant-refrigerant heat exchanger
Implementation Method 3
the hot-water supply refrigeration cycle and the hot-water supply load are cascade-connected so as to perform heat exchange between the hot-water supply refrigerant and the water in the heat medium-refrigerant heat exchanger
Implementation Method 4
perform heat exchange between the hot-water supply refrigerant and the water in the heat medium-refrigerant heat exchanger
Implementation Method 5
transmit the heat medium to said bypass pipe to increase the temperature of the volume of the heat medium which is equivalent to a volume of water held in said heat medium-refrigerant heat exchanger
Data Source
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AI summary
To provide an air-conditioning hot-water supply complex system that can simultaneously cover a cooling load, a heating load and a high-temperature hot-water supply load, thus can provide a stable heat source throughout the year, and allows rapid rise from startup. The air-conditioning hot-water supply complex system 100 includes a bypass pipe 303 connecting a portion between a heat medium-refrigerant heat exchanger 51 and a hot water storage tank 32 and a portion between the hot water storage tank 32 and a water circulation pump 31, in a water circuit of a hot-water supply load 3b.