【Mechanical Equipment Technology Edition】Daily Question 201708022: Describe the problem based on the image – 15-20 points of reward! !
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Starting today, in order to enhance communication among those interested in marine equipment, we have launched the 【Question of the Day】 initiative on the Mechanical Equipment Technology forum. We hope everyone will participate actively so as to progress and improve together! ! ! Participation earns 5 points in wealth; reasonable arguments earn 15–20 points. The diagram below shows a portion of the refrigeration principle diagram for the cooling unit in a certain chlor-alkali plant. After the project was completed, performance analysis revealed that it fell far short of the expected results. The upper part is the liquid storage tank, and the lower part is the economizer. Brief description: Function of the economizer – it subcools the liquid supplied to the evaporator in the shell side, and provides gas to the compressor via the tube side (in short, it is a heat exchanger). Refrigerant used: R22. Structure of the economizer: Horizontal shell-and-tube type. Shell side: Used for the main supply of liquid to the evaporator. Tube side: A portion of the liquid is diverted from here, throttled to reduce pressure, and then exchanges heat with the main liquid stream to become gas, which is supplied to the compressor. Main topic: As indicated by the red circle in the figure below, this is the liquid inlet for the economizer. Is it advantageous for heat exchange to have the liquid flow in from above and out from above? Why? What should be done? Answer: The liquid enters from above and exits from above; the liquid in the shell side does not fill it completely, leaving a gas space that reduces the heat exchange area. Poor heat exchange can directly affect the evaporation performance of the evaporator and the gas replenishment efficiency of the compressor, thereby **reducing the energy efficiency of the refrigeration system! The main liquid supply method of feeding from below and discharging from above should be adopted! ================================ Event Promotion: Petrochemical Zone – “Creative Ideas for Energy Savings” event (the second phase is in full swing) http://bbs.hcbbs.com/thread-1666758-1-1.html (Source: Haichuan Chemical Industry Forum) 2017 Coal Chemical Industry Event – “My Technical Upgrades” http://bbs.hcbbs.com/thread-1786290-1-1.html (Source: Haichuan Chemical Industry Forum)
My personal opinion: Make the diameters the same
The liquid enters and exits from the top; the liquid in the shell side does not fill it completely, leaving a gas space that reduces the heat exchange area. Poor heat exchange can directly affect the evaporation efficiency of the evaporator and the charge air efficiency of the compressor, thereby **reducing the energy efficiency of the refrigeration system**. The main liquid supply method of bottom in and top out should be adopted.
It is not conducive to heat exchange; if the specific structure of the heat exchanger is the same as that of conventional heat exchangers, having inlet and outlet at the top will create problems.
When connecting the heat exchanger to the system, it is necessary to ensure that for the medium on the hot side, the flow is from top to bottom, while for the medium on the cold side, the flow is from bottom to top, in terms of the piping connections
Heat exchangers all have low inlet and high outlet, allowing the entire heat exchange chamber to be filled. I’ve never seen anyone achieve high levels of progress before
It is not conducive to heat exchange; a flow pattern with fluid entering from below and exiting from above should be adopted. Firstly, this facilitates the circulation of the coolant, and secondly, hot substances have lower density and rise upward, so using this flow pattern can improve the efficiency of heat exchange
Whether it is conducive to heat exchange mainly depends on the internal structure, but generally, heat enters from the bottom and exits from the top...
For shell-and-tube heat exchangers, liquid flow from the top in and out of the exchanger is not conducive to heat exchange; it can be changed to flow from the bottom in and out.
Gas enters from above and exits from below, while liquid enters from below and exits from above; this is true for both heat exchange equipment and insulation equipment；
For the economizer, the liquid enters from above and exits from above; it is difficult to fill the shell side with liquid, resulting in areas where gas exists, which reduces the heat exchange area and leads to poor cooling efficiency. It should be modified so that the liquid enters from below and exits from above