Method for cooling a process flow
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Solution Overview
Problem
Conventional cooling methods for process streams using auxiliary streams, such as liquefied nitrogen, face challenges with excessive temperature gradients in heat exchangers, leading to potential damage and reduced operational safety due to high thermal expansion forces, especially during the initial cooling phase from ambient temperature to 80 K.
Innovation Solution
The process stream is divided into substreams with regulatable flow rates, where only the first substream is cooled in the first and second heat exchangers, and subsequent substreams are mixed in, regulating flow rates to maintain temperature differences of no more than 10 K, thereby reducing thermal load and pressure drop, and ensuring the maximum temperature differential remains within safe limits for plate heat exchangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the process stream is cooled exclusively by the liquefied nitrogen high-pressure stream in the first cooling phase, then the cooling efficiency is improved, but the temperature gradient between process stream and auxiliary stream becomes excessively high, causing thermal expansion forces to damage the heat exchanger
Solution Approach 1:
The process stream is divided into two or more substreams with regulatable flow rates. Only the first substream is cooled by the auxiliary stream in both heat exchangers, while subsequent substreams are mixed into the cooled first substream and cooled again in the second heat exchanger. This segmentation allows the thermal load to be distributed and the temperature differential to be controlled within safe limits.
Solution Approach 2:
The flow rates of the substreams are regulated such that the temperatures of the process streams to be cooled in the second heat exchanger differ by not more than 10 K. By dynamically adjusting flow rate parameters, the temperature differential is maintained within the maximum permissible range for plate heat exchangers, preventing thermal expansion damage while preserving cooling efficiency.
2Reliability
If the temperature gradient in the heat exchanger is reduced to safe limits, then the operational safety is improved, but the cooling speed and efficiency decrease
Solution Approach 1:
The cooling process continues without interruption by continuously adjusting the flow rates of the substreams. The regulated flow rates ensure that the temperature differential remains within safe limits throughout the cooling process, maintaining both operational safety and continuous cooling action.
Solution Approach 2:
The system employs flow rate regulation mechanisms that respond to temperature conditions in the heat exchangers. By monitoring and adjusting the flow rates of substreams based on temperature differences, the system maintains optimal operating conditions that balance safety and cooling efficiency.
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 method effectively reduces the maximum temperature differential across heat exchangers, ensuring operational safety and efficiency by minimizing thermal stress on equipment, allowing for continuous operation without exceeding permissible temperature limits, even in helium refrigeration systems.
Implementation Method 1
the exchange of heat between the process stream and the auxiliary stream is effected in a first heat exchanger and a second heat exchanger connected downstream thereof
Implementation Method 2
The heat of evaporation from the liquefied nitrogen is about the same in terms of size as the difference in enthalpy of the nitrogen through saturated vapor to ambient temperature
Implementation Method 3
these heat exchanger types are sensitive to excessively high temperature gradients between the individual channels and can be damaged or destroyed by excessively high thermal expansion forces
Data Source
AI summary
A method of cooling a process stream with an auxiliary stream is described, wherein the exchange of heat between the process stream and the auxiliary stream is effected in a first heat exchanger and a second heat exchanger connected downstream thereof.