VRF HVAC Artificial Load Circuit for Extra Low Load Operation
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Solution Overview
Problem
HVAC systems, particularly Variable Refrigerant Flow (VRF) systems, face inefficiencies and inability to operate effectively in extra low load conditions due to limitations in compressor speed ranges, leading to inefficient operation and rapid power cycling.
Innovation Solution
A VRF system design that includes a compressor, valves, expansion valves, and a controller to manage refrigerant flow and compressor speed, allowing for operation in extra low load conditions by creating artificial heating or cooling loads through the use of outdoor coils, enabling continuous operation at low compressor speeds and matching demand more accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the compressor operates at low speeds to match low cooling demand, then energy efficiency is improved, but the compressor cannot maintain stable operation and experiences rapid power cycling
Solution Approach 1:
The patent introduces an artificial cooling load circuit as an intermediary element. This circuit includes a cooling coil and expansion valve that create additional cooling demand, allowing the compressor to operate at higher speeds while still meeting the actual building's lower cooling requirements. The excess cooling capacity is dissipated through the artificial load, preventing compressor short cycling and maintaining stable operation.
Solution Approach 2:
The system changes the operating parameters of the compressor by dynamically adjusting its speed based on actual cooling demand. When building cooling demand is low, the compressor operates at reduced speeds to match the load, improving energy efficiency. When demand increases or the artificial load is activated, the compressor speed is increased to prevent unstable operation. This dynamic parameter adjustment resolves the contradiction between efficiency and stability.
2Reliability
If the compressor operates at high speeds to maintain stable operation, then reliability is improved, but energy efficiency deteriorates due to excessive cooling capacity for low demand
Solution Approach 1:
The patent segments the cooling load into two parts: the actual building cooling demand and an artificial cooling load. The artificial load is created through a separate circuit with a cooling coil and expansion valve. This segmentation allows the compressor to operate at speeds appropriate for total system capacity while only delivering the required amount to the building, with the excess being dissipated through the artificial load path.
Solution Approach 2:
The artificial cooling load circuit serves as an intermediary that absorbs excess cooling capacity. By introducing this intermediate element, the system can maintain the compressor at higher, more stable operating speeds without wasting excessive energy on unnecessary high-speed operation, as the artificial load provides a controlled pathway for the excess capacity.
3Adaptability or versatility
If the system uses multiple valves and coils to create artificial load, then adaptability to low load conditions is improved, but device complexity increases
Solution Approach 1:
The outdoor coils are designed to serve multiple functions: they act as the primary cooling coils for the building during normal operation, and simultaneously serve as components in the artificial cooling load circuit when needed. The same physical hardware performs different roles based on system demands, eliminating the need for completely separate artificial load equipment and reducing overall system complexity.
Solution Approach 2:
The patent merges the artificial cooling load circuit with the existing HVAC system components. The artificial load shares the compressor, refrigerant lines, and outdoor coil infrastructure with the primary building cooling system. This consolidation approach allows the system to gain adaptability for low-load operation while minimizing the increase in device complexity by reusing existing components rather than adding entirely separate 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
Enables efficient operation in both low and regular load conditions, providing flexible climate control and extending compressor lifespan by avoiding short cycling, thus improving overall system performance and reliability.
Implementation Method 1
a compressor operable to compress refrigerant
Implementation Method 2
a first expansion valve coupled to the first coil, a second expansion valve further coupled to a third coil
Implementation Method 3
a first valve coupled to the compressor and coupled to a first coil, a second coil, and a third coil
Data Source
AI summary
A system comprising a compressor, a first valve coupled to the compressor and to a first coil, a first expansion valve coupled to the first coil, and a second expansion valve. The second expansion valve coupled to a second coil. A second valve is coupled to the second coil and the compressor. A third valve is coupled to the compressor and a third coil. In response to receiving a heating demand that is below a threshold heating demand, a controller induces an artificial heating demand.