Two-Stage Heat Pump Compression With Oil Balance and Bypass Control
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Solution Overview
Problem
Existing heat pump systems face inefficiencies in meeting varying heating demands, particularly when the primary compressor cannot keep up, and there is a need for improved operational control and oil management in multi-compressor configurations.
Innovation Solution
A heat pump system featuring two hermetic compressors connected in series with independent operation, electronically controlled expansion valves, and oil separators for efficient oil recycling, along with a control unit to manage compressor speed and bypass functionality, ensuring optimal performance and oil balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single primary compressor is used, then the system structure is simple, but the system cannot meet varying heating demands efficiently
Solution Approach 1:
The single compressor is segmented into two separate compressors (first and second compressors) that can operate independently or together. This allows the system to adapt to varying heating demands by activating only one compressor for low demand or both compressors for high demand, thereby improving heating demand adaptability while maintaining manageable system complexity through modular architecture.
2Productivity
If two compressors are connected in series, then two-stage compression improves performance, but oil management becomes complex
Solution Approach 1:
The oil management system is segmented by providing separate oil separators for each compressor instead of a single shared oil separator. Each oil separator is dedicated to its corresponding compressor, simplifying oil management by eliminating the need for complex inter-compressor oil balancing while maintaining efficient two-stage compression performance.
3Ease of operation
If compressors share a common oil sump, then oil recycling is simplified, but oil level balancing becomes difficult
Solution Approach 1:
The common oil sump is segmented into separate oil separation systems for each compressor. Each compressor has its own dedicated oil separator that returns oil directly to its own compressor, eliminating oil level balancing issues between compressors while maintaining efficient oil recycling within each compressor system.
4Adaptability or versatility
If the primary compressor operates at fixed speed, then the control system is simple, but the system cannot adapt to varying loads efficiently
Solution Approach 1:
The compressors are equipped with variable speed drives that enable dynamic speed adjustment based on heating demand. The control system can independently or jointly control the speed of the first and second compressors, allowing efficient adaptation to varying loads while maintaining manageable control complexity through coordinated operation.
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 allows for efficient two-stage compression and adaptive operation based on demand, maintaining oil balance and enhancing overall system efficiency and performance across different heating loads and ambient conditions.
Implementation Method 1
A first oil separator is arranged behind the first hermetic compressor and is connected with the first hermetic compressor via a first oil conduit for feeding back oil from the first oil separator to the first hermetic compressor
Implementation Method 2
A first expansion valve is arranged in flow direction in front of the evaporator
Implementation Method 3
The first compressor and the second compressor are connected in series via a first conduit segment, such that the compression is a two-stage compression when the first and second compressor are both operated
Data Source
Figure 1
AI summary
A heat pump system is provided comprising a first and a second hermetic compressor (C1, C2), a condenser (2), a first electronically controlled expansion valve (19) and an evaporator (3). The first compressor and the second compressor (C1, C2) are connected in series via a first conduit segment (100), such that the compression is a two-stage compression when the first and second compressor (C1, C2) are both operated. A first oil separator (25) is arranged behind the first hermetic compressor (C1) and is connected with the first hermetic compressor (C1) via a first oil conduit (101) for feeding back oil from the first oil separator (25) to the first hermetic compressor (C1). A second oil separator (26) is arranged behind the second hermetic compressor (C2) and is connected with the second hermetic compressor (C2) via a second oil conduit (102) for feeding back oil form the second oil separator (26) to the second hermetic compressor (C1). A control unit is coupled to the first expansion valve (19) for electrically controlling the valve (19). The first expansion valve (19) is arranged in flow direction in front of the evaporator. A second expansion valve (9) is located within a second conduit segment (109) and is connected to the first conduit segment (100). The first and/or second hermetic compressor (C1, C2) is a variable speed compressor. At least one of the first and second compressors (C1, C2) is operable independently. The compressor which is not operated is bypassed via a bypass conduit (122, 123).