Energy saturated steam

The CHP plant which replaced these two separate energy supplies is based on a Ruston TB gas turbine (rated at 3.65 MW) which can meet the electrical demand of 3.2 MW and is connected to the grid so that excess electrical power can be sold. By providing full gas power, up to 12 t/h of saturated steam can be produced at 191°C and 13 bar. Five supplementary gas burners can be engaged to increase the steam... 

As an example of a negative heat capacity we have the specific heat of saturated steam. If unit mass of steam in the condition of saturation is raised one degree in temperature, and at the same time compressed so as to keep it just saturated at each temperature, it is found that heat is evolved, not absorbed, because the work spent in the compression exceeds the increase of intrinsic energy. 

From here the water mixture rises through the water-wall tubes (generator tubes) that constitute the furnace membrane where steam is generated (primarily by radiant energy transfer). The steam-BW mixture is collected in top water-wall headers and conducted through risers (riser tubes) back to the top drum, where the saturated steam separates from the water at the steam-water interface. 

To act as an efficient sterilizing agent, steam should be able to provide moisture and heat efficiently to the article to be sterilized. This is most effectively done using saturated steam, which is steam in thermal equilibrium with the water from which it is derived, i.e. steam on the phase boundary (Fig. 20.5). Under these circumstances, contact with a cooler surface causes condensation and contraction drawing in fresh steam and leading to the immediate release ofthe latent heat, which represents approximately 80% ofthe heat energy. In this way heat and moisture are imparted rapidly to articles being sterilized and dry porous loads are quickly penetrated by the steam. 

If a multiple-effect evaporator system produces 10 pounds of fresh water per pound of saturated steam at 35 p.s.i.a. (t = 259° F.) and t0 = 70° F., the work equivalent per 1000 gallons of fresh water is 60 kw.-hr. and the energy efficiency using the differential process with 50% recovery as the standard, is 6.9%. This calculation assumes that the available heat is simply the latent heat of condensation at the constant temperature of 259° F. 

Example 5.5 An inventor claims to have devised a process which takes in only saturated steam at 100°C and which by a complicated series of steps makes heat continuously available at a temperature level of 200°C. He claims further that, for every kilogram of steam taken into the process, 2,000 kJ of energy as heat is liberated at the higher temperature level of 200°C. Show whether or not this process is possible. In order to give the inventor the benefit of any doubt, assume cooling water available in unlimited quantity at a temperature of 0°C. 

Two pounds (0.9 kg) of saturated steam at 120 psia (827.4 kPa) with 80 percent quality undergoes nonflow adiabatic compression to a final pressure of 1700 psia (11,721.5 kPa) at 75 percent compression efficiency. Determine the final steam temperature T2, change in internal energy AE, change in entropy AS, work input W, and heat input Q. 

Example 3.6 Energy dissipation in a mixer In a mixer, we mix a saturated steam (stream 1) at 110°C with a superheated steam (stream 2) at 1000 kPa and 300°C. The saturated steam enters the mixer at a flow rate 1.5 kg/s. The product mixture (stream 3) from the mixer is at 350kPa and 240°C. The mixer loses heat at a rate 2kW. Determine the rate of energy dissipation if the surroundings are at 300 K. 

In a steady-state mixing process, 50.25 kg/s of saturated steam (stream 1) at 501.15 K is mixed with 7.363 kg/s of saturated steam (stream 2) at 401.15 K. The mixer is well insulated and adiabatic. Determine the energy dissipation (work loss) if the surroundings are at 298.15 K. 

A hydrocarbon mixture is distilled, producing a liquid and a vapor stream, each with a known or calculable flow rate and composition. The energy input to the distillation column is provided by condensing saturated steam at a pressure of 15 bar. At what rate must steam be supplied to process 2000 mol/h of the feed mixture ... 

Columns 5 and 6. The specific internal energies, f (kJ/kg), of saturated liquid water and saturated steam at the given temperature relative to a reference state of liquid water at the triple point. (Remember, we can never know the absolute value of internal energy or enthalpy, but only how these quantities change when the substance goes from one stale to another—in this case, from the reference state to the states listed in the table.)... 

Determine the vapor pressure, specific internal energy, and specific enthalpy of saturated steam... 

Steam at 10 bar absolute with 190 C of superheat is fed to a turbine at a rate m = 2000 ke/h. The turbine operation is adiabatic, and the effluent is saturated steam at 1 bar. Calculate the work output of the turbine in kilowatts, neglecting kinetic and potential energy changes. 

A fuel oil is burned with air in a boiler furnace. Tlie combustion produces 813 kW of thermal energy, of which 65% is transferred as heat to boiler tubes that pass through the furnace. The combustion products pass from the furnace to a stack at 650 C. Water enters the boiler tubes as a liquid at 20 C and leaves the tubes as saturated steam at 20 bar absolute. 

Liquid water is fed to a boiler at 24 C and 10 bar and is converted at constant pressure to saturated steam. Use the steam tables to calculate Ai (kJ/kg) for this process, and then calculate the heat input required to produce 15,000 m /h of steam at the exiting conditions. Assume that the kinetic energy of the entering liquid is negligible and that the steam is discharged through a l5-cm ID pipe. 

An inventor has developed a complicated process for making heat continuously available at an elevated temperature. Saturated steam at 373.15 K (100°C) is the only source of energy. Assuming that there is plenty of cooling water available at 273.15K (0°C), what... 

All evaporators remove a solvent vapor from a liquid stream by means of an energy input to the process. The energy source is most usually dry and saturated steam, but can be a process heating medium such as liquid or vapor phase heat transfer fluids (Dowtherm or Therminol), hot water, combustion gases, molten salt, a high temperature process stream, or, in the case of a solar evaporation plant, radiation from the sun. 

Modern distillation plants have unit capacities of about 25,000 t/d. The energy consumption is approximately 95 KWh/to distillate in the form of saturated steam of a pressure of about 2.2 bar and 4 to 5 KWh/to distillate in form of power for the pump drives. All distillation processes produce a distillate containing only 20 to 30 ppm salts (total dissolved solids). Reverse osmosis (RO) will be the alternative to distillation. The modules which are successfully employed are of the "spiral wound" or the "hollow fiber" configuration. Under favorable conditions, the economic service lifetime of the modules resp. the membranes is about 5 years and warranties for such a figure are given by manufacturers. 

The liquid of a tank is heated with saturated steam, which flows through a coil immersed in the liquid (Figure 10.2). The energy balance for the system yields... 

Thermal damage to biological systems is caused by absorption of heat energy. Well-controlled laboratory studies show that when pure cultures of microorganisms are held in saturated steam at a constant sterilizing temperature there arc linear relationships between the logarithm of the number of survivors and the time of exposure (exponential inactivation). 

As with sterilization by saturated steam, thermal damage to biological systems as a result of dry heat sterilization processes is a function of absorbtion of heat energy. Inactivation of microorganisms is by oxidation. The kinetics of oxidation and population death approximate to first-order reactions, but they are significantly different from the processes of coagulation of cellular proteins found with moist heat sterilization in that they require far higher temperatures and proceed more slowly. 

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