Two-stage compressor having variable speed first stage
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Solution Overview
Problem
Air source heat pumps face significant impairments in heating operations at low ambient temperatures, requiring additional compressor capacity to maintain efficiency and capacity, which existing systems struggle to provide effectively.
Innovation Solution
A two-stage compressor system with a variable-speed first stage and an optional second compressor, controlled by variable-frequency drives, allows for efficient operation by matching pressure ratios and integrating additional capacity for high-lift heating operations, using a bypass line and flow reverser to selectively engage or bypass compressors based on mode and demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single compressor is used for regular cooling operations, then the device complexity is reduced, but the heating capacity and efficiency at low ambient temperatures deteriorates
Solution Approach 1:
The compressor system is segmented into two independent compressors: a first compressor optimized for regular cooling operations and a second compressor specifically for high-lift heating operations. This segmentation allows each compressor to be sized and configured for its specific function, improving heating reliability at low temperatures without requiring the first compressor to be oversized for all conditions.
Solution Approach 2:
The second compressor is designed with multi-functionality to serve dual purposes: it provides high-lift capacity for heating operations at low ambient temperatures and can also contribute to cooling capacity when needed. This universal design allows a single component to address multiple system requirements.
2Reliability
If the first compressor is sized for high-lift heating operations, then the heating capacity at low temperatures is improved, but the cooling efficiency at moderate temperatures deteriorates
Solution Approach 1:
The system segments the compression functions by dedicating the first compressor to regular cooling operations where it operates at optimal efficiency, while the second compressor handles high-lift heating operations. This prevents the first compressor from being oversized and operating inefficiently during moderate-temperature cooling.
Solution Approach 2:
The system changes operational parameters by using the second compressor specifically when high pressure ratios are required for low-temperature heating, while the first compressor maintains its optimal operating parameters for regular cooling. This parameter-based allocation optimizes efficiency across different operating conditions.
3Reliability
If a second compressor is added for high-lift operations, then the heating capacity at low temperatures is improved, but the device complexity increases
Solution Approach 1:
The second compressor is designed as a multi-functional component that provides high-lift heating capacity when needed and can also contribute to cooling capacity. This universal design justifies the added complexity by providing versatile functionality that addresses multiple system requirements with a single component.
Solution Approach 2:
The control system acts as an intermediary that intelligently manages the complexity of operating two compressors. It automatically determines when to engage the second compressor based on ambient temperature and heating load conditions, and coordinates their operation to optimize system performance while simplifying user interaction.
4Reliability
If the first compressor operates at high speed for high-lift heating, then the heating capacity is improved, but the energy efficiency deteriorates
Solution Approach 1:
The system segments the high-lift heating function to the second compressor, which is specifically sized and configured for high-pressure-ratio operation. This allows the first compressor to operate at moderate, efficient speeds for regular conditions, while the second compressor handles the high-speed, high-capacity requirements when ambient temperatures are low.
Solution Approach 2:
The system changes the operational parameters by allocating high-speed operation to the second compressor during low-temperature heating, while the first compressor maintains efficient operating parameters. This parameter allocation ensures that high energy consumption is confined to conditions where it is necessary for adequate heating capacity.
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 operation across varying ambient temperatures by optimizing compressor usage, ensuring adequate capacity for heating and cooling, thus enhancing the overall performance and efficiency of HVACR systems.
Implementation Method 1
the first compressor includes a variable-frequency drive, and the HVACR system includes a bypass line and one or more valves configured such that the first compressor can be selectively bypassed
Implementation Method 2
the HVACR system includes a bypass line and one or more valves configured such that the first compressor can be selectively bypassed
Implementation Method 3
the flow reverser has a heating operation position and a cooling operation position
Implementation Method 4
the controller is configured to determine an operating speed for the first compressor and control the variable-frequency drive to operate the first compressor at the determined operating speed
Data Source
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AI summary
A compressor driven by a variable-frequency drive (VFD) is provided to supplement operation of another compressor of a heating, ventilation, air conditioning, and refrigeration (HVACR) system, such as heat pump operations at low ambient temperatures. The VFD is controlled to provide efficient pressure ratios for each compressor of the HVACR system when the compressor driven by the VFD is used to supplement the other compressor. The compressor driven by the VFD can be included as a built-in compressor of the HVACR system or added subsequently as part of a booster package.