Hot gas defrost in a cooling system
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Solution Overview
Problem
Existing cooling systems with hot gas defrost cycles require large piping due to a small pressure difference between the hot gas supply and return, leading to increased material costs and space occupancy, as they need a stepper valve to maintain pressure.
Innovation Solution
A cooling system with a parallel compressor configuration that increases the pressure difference between hot gas supply and return, eliminating the need for a stepper valve and allowing for reduced piping size by cycling refrigerant from a low temperature compressor to a medium temperature compressor after defrosting a low temperature load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a stepper valve is used to maintain pressure in hot gas defrost cycles, then the pressure difference between hot gas supply and return is maintained, but the piping size must be large to limit pressure drop
Solution Approach 1:
The patent changes the pressure parameter by introducing a parallel compressor that increases the pressure of hot gas returning from the defrost cycle. This creates a larger pressure differential between supply and return, allowing smaller piping dimensions while maintaining adequate flow rates and limiting pressure drop across the system.
2Stress or pressure
If large piping is used to limit pressure drop, then the pressure difference is maintained, but material cost and space occupancy increase
Solution Approach 1:
By modifying the pressure parameter through the parallel compressor configuration, the system achieves adequate pressure differential with reduced piping dimensions. This directly reduces the quantity of materials required for piping installation, lowering both material costs and space occupancy while maintaining the necessary pressure difference for effective hot gas defrost operation.
3Stress or pressure
If large piping is used to limit pressure drop, then the pressure difference is maintained, but the system footprint increases
Solution Approach 1:
The parallel compressor configuration changes the pressure parameter to create sufficient pressure differential, enabling the use of compact piping with smaller cross-sectional area. This reduces the space required for piping installation, thereby decreasing the overall system footprint while maintaining effective hot gas defrost functionality.
4Reliability
If a stepper valve is used to maintain pressure, then the hot gas defrost cycle functions, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the stepper valve from the system by using a parallel compressor configuration that naturally maintains the required pressure differential through compression. This removes the complex valve mechanism while preserving the hot gas defrost cycle functionality, thereby reducing device complexity.
5Quantity of substance
If smaller piping is used, then material cost and space occupancy decrease, but pressure drop increases
Solution Approach 1:
The parallel compressor configuration changes the pressure parameter by increasing the pressure of returning hot gas. This compensates for the increased pressure drop that would occur in smaller piping, allowing the system to use compact piping with reduced material cost and space occupancy while maintaining adequate pressure differential for effective defrost 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 reduces the size and cost of piping, decreases the system's footprint, and potentially lowers the refrigerant charge and flash tank size, while maintaining efficient defrosting capabilities.
Implementation Method 1
A cooling system with a parallel compressor configuration that increases the pressure difference between hot gas supply and return
Implementation Method 2
cycling refrigerant from a low temperature compressor to a medium temperature compressor after defrosting a low temperature load
Data Source
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AI summary
A system (100) includes a high side heat exchanger (105), a first load (120), a second load (115), a first compressor (130), a second compressor (125), and a third compressor (205). The high side heat exchanger (105) removes heat from a refrigerant. The first load (120) uses the refrigerant to remove heat from a first space proximate the first load (120). The second load (115) uses the refrigerant to remove heat from a second space proximate the second load (115). The first compressor (130) compresses the refrigerant from the first load (120) and sends the refrigerant to the first load (120). The refrigerant defrosts the first load (120). The second compressor (125) compresses the refrigerant from the second load (115) and the refrigerant from the first load (120) that defrosted the first load (120). The third compressor (205) compresses the refrigerant from the first compressor (130).