Steam System

3. Steam System

3. STEAM SYSTEM

Syllabus Steam System: Properties of steam, Assessment of steam distribution losses, Steam leakages, Steam trapping, Condensate and flash steam recovery system, Identifying opportunities for energy savings.

3.1 Introduction

Steam has been a popular mode of conveying energy since the industrial revolution. Steam is used for generating power and also used in process industries such as sugar, paper, fertilizer, refineries, petrochemicals, chemical, food, synthetic fibre and textiles The following characteristics of steam make it so popular and useful to the industry: Highest specific heat and latent heat Highest heat transfer coefficient Easy to control and distribute Cheap and inert

3.2 Properties of Steam

Water can exist in the form of solid, liquid and gas as ice, water and steam respectively. If heat energy is added to water, its temperature rises until a value is reached at which the water can no longer exist as a liquid. We call this the "saturation" point and with any further addition of energy, some of the water will boil off as steam. This evaporation requires relatively large amounts of energy, and while it is being added, the water and the steam released are both at the same temperature. Equally, if steam is made to release the energy that was added to evaporate it, then the steam will condense and water at same temperature will be formed. Liquid Enthalpy Liquid enthalpy is the "Enthalpy" (heat energy) in the water when it has been raised to its boiling point to produce steam, and is measured in kCal/kg, its symbol is hf. (also known as "Sensible Heat")

The heat required to change the temperature of a substance is called its sensible heat. If 1 kg of water in a vessel at 25oC i.e. containing heat value of 25 kcals is heated by adding 75 kcals, the water is brought to boiling point of 100 oC. To change the water to steam an additional 540 kcal would be required. This quantity of heat required to change a chemical...