Low pressure chiller
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Solution Overview
Problem
Low pressure refrigerants in HVAC systems offer better thermodynamic cycle performance but are hindered by heat transfer disadvantages and require larger vapor spaces and pipes, increasing costs and volumetric footprint.
Innovation Solution
The implementation of a falling film evaporator and economizer assembly with shared walls to optimize heat transfer performance, reduce refrigerant vapor flow resistance, and eliminate unnecessary piping connections, using a low pressure refrigerant like R245fa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low pressure refrigerants are used, then thermodynamic cycle performance is improved, but heat transfer performance deteriorates
Solution Approach 1:
The economizer assembly and condenser are merged into a single integrated component sharing a common wall, eliminating the need for external piping and reducing refrigerant transport losses. This integration improves heat transfer efficiency by direct contact between refrigerant streams while maintaining the thermodynamic advantages of low pressure refrigerants.
Solution Approach 2:
The falling film evaporator transitions from conventional internal flow heat transfer to external film flow over tube surfaces, dramatically increasing the heat transfer surface area and coefficient. This dimensional change in heat transfer geometry compensates for the inherently lower heat transfer coefficients of low pressure refrigerants.
2Use of energy by moving object
If low pressure refrigerants are used, then thermodynamic cycle performance is improved, but vapor space and pipe size increase
Solution Approach 1:
By integrating the economizer and condenser into a single assembly with shared walls and internal flow passages, the patent eliminates external piping requirements. The refrigerant flows directly through integrated passages from the economizer into the condenser, dramatically reducing the volumetric footprint while maintaining low pressure refrigerant benefits.
Solution Approach 2:
The economizer assembly is nested within or adjacent to the condenser structure, with the evaporator positioned below. This nested arrangement allows refrigerant to flow vertically through compact, space-efficient pathways, minimizing the overall system volume while accommodating the larger vapor spaces required by low pressure refrigerants.
3Ease of operation
If larger pipes and vapor spaces are used, then low pressure refrigerant flow is accommodated, but system cost and footprint increase
Solution Approach 1:
The integration of economizer, condenser, and evaporator into a compact assembled unit eliminates the need for large external pipes and multiple discrete components. The internal flow passages are designed to accommodate low pressure refrigerant vapor volumes within the compact structure, reducing both manufacturing complexity and system footprint.
Solution Approach 2:
The falling film evaporator configuration allows for compact horizontal tube arrangements that maximize heat transfer surface area within a small vertical footprint. This dimensional optimization accommodates refrigerant flow requirements without proportionally increasing system volume or cost.
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 enhances heat transfer efficiency, reduces system footprint, and lowers costs by optimizing the aspect ratio of condenser and evaporator components and ensuring continuous liquid feed, while maintaining thermodynamic cycle performance gains.
Implementation Method 1
a condenser to condense a flow of refrigerant into a liquid state
Implementation Method 2
A falling film evaporator exchanges thermal energy between the liquid refrigerant and a medium flowed through a plurality of evaporator tubes in the evaporator
Implementation Method 3
an economizer assembly having at least one separator chamber to separate liquid refrigerant from vapor refrigerant
Data Source
AI summary
A heating, ventilation and air conditioning (HVAC) system includes a condenser to condense a flow of refrigerant into a liquid state. The system further includes an economizer assembly having at least one separator chamber to separate liquid refrigerant from vapor refrigerant. The economizer assembly shares an upper common wall with at least a portion of the condenser and the flow of refrigerant from the condenser into the economizer assembly proceeds through a flow opening in the upper common wall. A falling film evaporator exchanges thermal energy between the liquid refrigerant and a medium flowed through a plurality of evaporator tubes in the evaporator.