The heating efficiency of heat exchange equipment (such as steam heaters and heat exchangers) is affected by multiple factors such as steam quality, condensate discharge, and system sealing, among which the exhaust function of the drain valve is a key link. By optimizing the exhaust function, the heating efficiency can be effectively improved by 5% to 15%. The specific method is as follows:
1、 Quickly eliminate non condensable gases and reduce thermal resistance
Steam often contains air (such as residual during system start-up) or carbon dioxide (generated by the dissolution of condensed water), which are non condensable gases that accumulate on the heat exchange surface to form a gas film, resulting in a 30% to 50% increase in thermal resistance.
Solution: Choose a drain valve with an automatic exhaust valve (such as a thermal static type or bimetallic plate), which has a built-in exhaust device that can automatically open when the steam pressure is ≥ 0.01MPa, and quickly discharge gas (exhaust rate ≥ 0.5m ³/h).
Case: After the renovation of a steam heat exchanger in a food factory, the exhaust time was shortened from 15 minutes to 3 minutes, and the heating efficiency was improved by 8%.
2、 Accurate control of condensate discharge to maintain steam dryness
The accumulation of condensed water will reduce the dryness of steam (increase the moisture content), resulting in a decrease in the heat transfer coefficient. The drain valve should be discharged in a timely manner during the initial stage of condensate formation (undercooling of 2-5 ℃), while avoiding steam leakage.
Optimization measures:
Selection and matching: Select the displacement of the drain valve based on the load of the heat exchanger (usually 1.2-1.5 times the amount of condensate), to avoid steam waste caused by "big horses pulling small cars".
Installation position: Install the drain valve at the low point of the heat exchanger to ensure that condensed water flows naturally into the valve chamber and reduce air resistance.
3、 Dynamically respond to load changes and stabilize steam pressure
When the load of heat exchange equipment fluctuates (such as the start and stop of a production line), sudden changes in steam flow can easily cause pressure fluctuations in the system, affecting heating uniformity.
Technical upgrade: Adopting an adjustable thermal power drain valve, the action pressure is changed by adjusting the spring preload force to adapt to load changes (adjustment range ± 20%).
Effect: After the application of the heat exchange system in a chemical enterprise, the pressure fluctuation decreased from ± 0.1MPa to ± 0.03MPa, and the product qualification rate increased by 12%.
4、 Regularly maintain the exhaust function to prevent failure
The exhaust hole of the drain valve is easily blocked by particulate matter (such as rust and welding slag), resulting in poor exhaust.
Maintenance points:
Monthly dismantling inspection: Clean the exhaust hole and valve core, and blow them with compressed air (pressure ≤ 0.3MPa).
Online monitoring: Install a pressure sensor, and when the pressure in front of the valve remains 0.05MPa higher than the system pressure, it will prompt the need for maintenance.
Comprehensive benefits: By optimizing the exhaust function of the drain valve, the thermal efficiency of the heat exchange equipment can be improved to over 90%, while reducing steam consumption by 10% to 20%, saving energy costs of over one million yuan per year (taking medium-sized factories as an example).