Best practice no.20

Number 20

September 2023

BEST

Manufacturing Engineering PRACTICE

STEAM TITLE

The vapor titer serves to measure the percentage by mass of vapor in liquid-vapor and is usually denoted with the letter X , expresses the kilograms of dry saturated vapor in one kilogram of wet saturated vapor. According to this definition, in one kilogram of wet saturated steam there will be “x” kilograms of dry steam and 1 -x kilograms of saturated liquid. Therefore, a dry vapor will have a titer of 1 and a saturated liquid will have a titer of 0.

STEAM TITLE

TYPES OF CALORIMETERS

The value of “x” varies from zero (saturated liquid) to 1 (saturated vapor) . For titer values close to 1, we have a small mass of liquid in the form of droplets in suspension.

For lower values, the liquid settles on the bottom of the container due to the effect of gravity.

It is very normal that, in a mixture of saturated liquid and vapor, the mass of each phase is usually unknown, in which case, the volumes can be related, and the titer would be defined as a relationship between the increase in volume during vaporization and the increase of volume that would correspond to dry steam at the same pressure.

Where: V x = is the specific volume of the mixture V L = is the specific volume of the saturated liquid V i = is the specific volume of saturated vapor

Types of calorimeters.

Separation calorimeter . They are based on separating humidity from the humid vapor that enters the device. In this case it is necessary to measure the weight of the moisture collected in the form of water and the weight of the dry vapor leaving the calorimeter. Separation type calorimeters are used to determine the titer of vapors and low pressure vapors.

The title expression in decimal fraction form is:

Where:

M ds = weight of dry vapor passing through the calorimeter, kg or lb m m = weight of moisture separated from M ds of kg or lb of dry steam, in kg or lb X = calidad del vapor

FOR-IM-024

REVISION DEL FORMATO: C

FECHA DE EFECTIVIDAD DEL FORMATO:10/03/2022

Choking or reheating calorimeter (Ellison) . They are because, if the steam is throttled and then expands without doing work or losing heat, the total energy of the steam remains unchanged. Radiation losses must be reduced to a minimum and to do so, the calorimeter and the duct connecting to the steam pipe must be completely thermally insulated. The steam enters through the sampling nozzle and expands as it passes through an orifice, enters the vapor chamber, finally escaping through the upper part. Momentary excess moisture is separated and re-evaporated within the vapor chamber, and the effect is indicated in direct proportion by the superheat thermometer located in the vapor path. To know the initial pressure of the steam, you need to use a manometer.

The expression for the vapor titer can be stated as the total enthalpy of the wet saturated vapor before expansion ( h f + Xh fg ) is equal to the total enthalpy h of the superheated steam after expansion.

Where:

X = steam quality, expressed as a decimal fraction. h = total enthalpy of superheated steam at the absolute pressure of the calorimeter, in kcal/kg or BTU/lb h f = enthalpy of the liquid at the initial pressure, in kcal/kg or BTU/lb h fg = enthalpy of vaporization of dry saturated steam at initial absolute pressure, in kcal/kg or BTU/lb

If we have a boiler that works at 6.5 kg/cm² gauge

Then:

calorimeter mass............................................. : 11.682 kg Calorimeter mass + water ............................... : 22.370 kg Calorimeter mass + water + water vapor......... : 23.218 kg mass of water ( m H2O )....................................... : 10.688 kg steam mass ( m v )............................................. : 0.848 kg Fina Mass l ( m f ).............................................. : 11.536 kg

Enthalpy of water at a temperature of 15°C (ambient): ( U H2O ) 15.04 kcal/kg Final enthalpy of water: ( U f ) 61 kcal/kg

To calculate h have :

h f = 165.6 kcal/kg h fg = 493.9 kcal/kg

calculated X

This means that the titration or quality of the steam will be 96.11% dry steam and 3.89% will be humidity.

FOR-IM-024

REVISION DEL FORMATO: C

FECHA DE EFECTIVIDAD DEL FORMATO:10/03/2022