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Arduino FreeRTOS Mutex Examples

In this section, we will explain using an example to demonstrate mutexes in Arduino using freeRTOSThere are two freeRTOS Mutex examples in this tutorial, the first example demands some hardware (LCD) While the second does not need any hardware, you can try out both if you have the resources.

In the last tutorial, we considered in detail: semaphores and mutexes and we also established the difference between binary semaphores and mutexes.
Just for a review:Recall that a mutex is a locking mechanism that implements the take and gives functionality in itself, unlike a binary semaphore. See this tutorial if you have not before continuing.
Example 1: Protecting the LCD Resource Using Mutex in freeRTOS
Program Description

In this program, we Demonstrated the use a 16x2 LCD display to implement a mutex.

The LiquidCrystal library works with all LCD displays that are compatible with the Hitachi HD44780 driver. you can usually tell them by their 16-pin interface.


* LCD RS pin to digital…

Feed Water Heaters: Relevance in a Power Plant

In this post, we will be considering the relevance of feedwater heaters in a typical power plant. What are they? Why should there be feed water heaters? What advantages do they add to the system? What happens when they are not present?

Feed water is the working fluid used for power production. The purified water that is sent into the boiler for heating and for the steam work process in the turbine after a series of treatments.

What are feedwater heaters?

Feedwater heaters are major pieces of equipment or passive machinery that help increase the temperature of the feedwater before introducing it into the hot well, to accurately understand this, you will need to go through the post on power generating process in a power plant.

Whenever we talk about heaters, three parameters are important.

  • Heat source

  • What is being heated

  • Heat transfer method

The working principle of feedwater heaters is basic, they work on the principle of heat conduction, heat is taken from the high-temperature extraction steam to the increase the temperature of the feedwater. This temperature increase is done gradually by different heater sections.

The heaters before the Boiler Feed Pump are called Low-Pressure heaters after the feed water has gained pressure through the action of the BFP (Boiler Feed Pump), the subsequent heaters after the BFP are called high-pressure heaters.

During my training experience, the feed water heaters I saw used extraction steam tapped from various sections of the turbine as a heat source, the feed water was being heated, the heat transfer is indirect, the heating element is not in direct contact with the feed water, instead is configured in a shell tube arrangement.

However, there are other pieces of equipment that perform the function of a feedwater heater through other means. One of which is the economizer, the economizer can be considered as a feed water heater that preheats the feed water but it uses a separate method of heating to do this, the flue gases (exhaust gases from combustion) is used to do the preheating this time. Another silent feedwater heater is the deaerator. Deareation can be accomplished by using deaerator heaters, vacuum deaerators, mechanical pumps, and steam-jet ejectors. Steam jet ejectors which I have seen. There are two subdivisions of Deaerating heaters: Spray type and tray type. You can read about them  Here.

Principle of Operation of the Deareator Heater

The deaerator operates as a direct-contact heater it is combined with the storage tank which serves as a reservoir of deaerated and heated water for water balance in the water-steam cycle of the power plant. The deaerator performs the function of spray, tray and reboiling in three processes:

  • Spraying of condensate at the top of the deaerator using nozzles.

  • Partial deaerating by passing through a number of trays.

  • Heating and further deaeration of the condensate water

  • By supplying continuous heat to the deaerated feedwater though hot water, steam or both, subsequently makes Oxygen-free feedwater available.

What are the relevance of feedwater heaters in a  typical thermal power plant?

The relevance of feedwater heaters in increasing the efficiency of the system cannot be overemphasized. In Fact, a failure of a heater can cause a system failure. In some power plants, heater failure is included in the MFT alarms. This set of alarms known as the MFT alarms can shut down the system if they occur.

How does the feed water increases the efficiency of the system? The feedwater heaters increase the efficiency of the system by gradually increasing the temperature of the feedwater (Preheating the feed water) before letting it into the boiler drum thus preventing thermal shock. Thermal shock is a situation that arises when there is a huge temperature gradient when mixing two substances that is introducing a low-temperature fluid into a high-temperature fluid(in the boiler), this entails that the boiler will do more work, and thus efficiency is reduced.

In a typical plant, the drain for higher temperature heater serves as the heating element for the following heater since it still has some heat energy left, when it has lost all its energy, it is further condensed and joins in the steam generation process. Thus the overall system efficiency is improved.


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