Centrifugal Chiller Compressor Control Across Low and High Loads
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Centrifugal chillers with a combination of variable-speed and constant-speed centrifugal compressors face inefficiencies at low and high compressor load factors, and existing solutions do not optimally enhance their performance, particularly in terms of energy savings and maintenance costs.
Innovation Solution
A centrifugal chiller system with a variable-speed centrifugal compressor and a constant-speed centrifugal compressor operating in parallel, where a control unit selects between a variable-speed compressor priority mode and a combined-use mode based on load factor, utilizing a sealing section to minimize refrigerant leakage and optimize compressor operation across varying load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If two variable-speed centrifugal compressors are provided, then efficiency enhancement is achieved across varying loads, but cost and maintenance complexity increase due to requiring two inverters
Solution Approach 1:
The invention merges the advantages of both variable-speed and constant-speed compressors into a single hybrid system. By combining one variable-speed compressor with one constant-speed compressor, the system achieves efficiency enhancement across varying loads without duplicating the expensive inverter equipment, thus reducing maintenance complexity and cost.
Solution Approach 2:
The constant-speed compressor serves as a universal backup and supplemental unit that can operate independently or in conjunction with the variable-speed compressor. This multi-functional arrangement allows the system to maintain efficiency across different operating conditions while avoiding the need for two full variable-speed systems with their associated inverters.
2Quantity of substance
If two constant-speed centrifugal compressors are provided, then sufficient capacity is achieved for high capacity applications, but efficiency enhancement cannot be expected at low compressor load factor
Solution Approach 1:
The compressor capacity is segmented between two constant-speed compressors to achieve sufficient total capacity for high-load applications. However, the system is designed so that only one compressor operates at a time based on load requirements, preventing the efficiency penalty that would occur if both constant-speed compressors operated simultaneously at low load factors.
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
The system achieves high efficiency across wide compressor load factors by switching between variable-speed and combined-use modes, reducing energy consumption and maintenance costs, while preventing refrigerant leakage and maintaining performance.
Implementation Method 1
a variable-speed centrifugal-compressor (7) whose rotational frequency can be varied by an inverter and compresses a refrigerant; a constant-speed centrifugal-compressor (8) connected in parallel with the variable-speed centrifugal-compressor (7) and operated at a constant rotational speed to compress the refrigerant
Implementation Method 2
a condenser (9) that condenses the refrigerant compressed by the variable-speed centrifugal-compressor (7) and/or the constant-speed centrifugal-compressor (8) into a liquid using cooling water supplied thereto
Implementation Method 3
an evaporator (11) that evaporates the refrigerant expanded by the expansion valve
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is a centrifugal-chiller including one variable-speed centrifugal-compressor and one constant-speed centrifugal-compressor and capable of high-efficiency operation. A centrifugal-chiller comprising a variable-speed centrifugal-compressor whose rotational frequency can be varied by an inverter and which compresses a refrigerant; a constant-speed centrifugal-compressor connected in parallel with the variable-speed centrifugal-compressor and operated at a constant rotational speed to compress the refrigerant; and a control unit that controls the operations of the variable-speed centrifugal-compressor and the constant-speed centrifugal-compressor, wherein in the case where a required load factor of the centrifugal-chiller is less than a predetermined value, the control unit selects a variable-speed-compressor priority operating mode in which only the variable-speed centrifugal-compressor is activated, and in the case where the required load factor of the centrifugal-chiller is the predetermined value or greater, the control unit selects a combined-use operating mode in which the variable-speed centrifugal-compressor and the constant-speed centrifugal-compressor are activated.