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How To Estimate Optimum Insulation Thickness

In previous post I shared how to estimate insulation thickness for both flat surface and cylindrical surface. In this post I want to share how to estimate optimum insulation thickness.

The total annual cost of insulation is the sum of the cost of heat energy lost and fixed cost. A plot of cost vs insulation thickness will determine the most economical insulation thickness. A dimensionless factor can be used to calculate insulation thickness, depending on the ratio of insulation thickness to pipe diameter in the following equation:

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Sizing and Horse Power Estimation of Counterflow Induced-Draft Cooling Tower

In this post I want to share to you how to do preliminary sizing and horse power estimation for counterflow induced-draft cooling tower. Calculation in this post parallel or cross-flow cooling tower. Also they do not apply when the approach to cold water temperature is less than 5oF (2.8oC).

Approach temperature is the temperature of the water leaving the cooling tower minus ambient wet bulb temperature.

[Read more: Assessment of Cooling Tower Performance]

To do this, we need this data:

  • Hot water temperature
  • Cold water temperature
  • Wet-bulb temperature
  • Water rate

Let’s start sizing the estimation. Let say we have cooling tower with the following process data:

  • Hot water temperature = 102oF
  • Cold water temperature = 78oF
  • Wet-bulb temperature = 70oF
  • Water rate = 1000 gallon per minute

Step 1: Find water concentration by using chart

Chart below is used to find water concentration, which is expressed in gallon per minute per square feet (gal/(min.ft2)).

When hot water temperature is 102oF and cold water temperature is 78oF, we get water concentration at around 2.8 gal/(min.ft2).

Step 2: Calculate required area of cooling tower

Required area of cooling tower is quantity of water circulated divided by water concentration = 1000/2.8 = 357.14 ft2.

Step 3: Find horsepower per area of cooling tower

Horsepower per area of cooling tower is estimated by using the following chart. Connecting the point representing 100 percent of standard tower performance with the turning point and extending this straight line to the horsepower scale show that it will give around 0.04 hp/ft2 of actual effective tower area. For a tower 357.14 ft2 (see Step 2), 14.6 hp is required to perform the necessary cooling.

Step 4: Check if commercial tower size is less than required area

Suppose the actual commercial tower size has an area of only 300 ft2. Within reasonable limit, the shortage of actual area can be compensated by increasing air velocity through the tower. This requires boosting fan horsepower to achieve 110 percent of standard tower performance. From chart in Step 3, we found the fan horse power is 0.057 hp/ft2 of actual area, or 0.057 x 300 = 17.1 hp.

Step 5: Check if commercial tower size is more than required area

On the other hand, if the actual commercial tower size is 370 ft2, the cooling equivalent to 357.14 ft2 of standard tower area can be accomplished with less air and less fan horsepower. From figure in Step 3, the fan horsepower for a tower operating at 90 percent of standard performance is 0.028 hp/ft2 of actual tower area, or 370 x 0.028 = 10.4 hp.

Reference:

Perry’s Chemical Engineers’ Handbook.

Hydrate Prediction using Vapor-Solid Equilibrium Constant

In previous post, hydrate in natural gas system can be estimated by two approaches, which are approximate method and analytical method. Approximate method used when gas composition is unknown. It uses pressure-temperature correlation to predict hydrate formation temperature.

In this post, I want to share how to predict hydrate formation using analytical method, which uses vapor-solid equilibrium constant. Vapor-solid equilibrium constant is expressed as below:

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Hydrate Prediction using Pressure-Temperature Correlation

A hydrate in natural gas system is a physical combination of water and other small molecules to produce a solid which has an “ice-like” appearance but has a different structure than ice. It resembles dirty ice but has voids into which gas molecules will fit. Most common compounds found in gas hydrate are water, methane, and propane, or water, methane, and ethane.

Hydrate formation in natural gas transmission pipeline
Hydrate formation in natural gas transmission pipeline

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Global Carbon Dioxide Emissions by Source

Carbon dioxide is one of key greenhouse gases. Primary source of carbon dioxide emission is the usage of fossil fuel. In addition, carbon dioxide can also be emitted from direct human-induced impacts on forestry and other land use, such as through deforestation, land clearing for agriculture, and degradation of soils.

In this post, I want to share global carbon dioxide emissions by source or by sector and by region. Data used in this post come from climatewatchdata.org with data source from CAIT (Climate Analysis Indicator Tools), which compiles data from peer-reviewed and internationally recognized greenhouse gas inventories developed by other government agencies worldwide.

In 2016, estimated worldwide carbon dioxide emissions total nearly 37 Giga tons. This number includes the effect of land use and forestry.

Global carbon dioxide emissions including land-use change and forestry
Global carbon dioxide emissions including land-use change and forestry

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Schematic of two-phase horizontal separator

Preliminary Sizing of Two-Phase Horizontal Separator

Separator is the initial processing vessel in any production facility. Therefore, it should be designed properly to prevent reduction of capacity of the entire facility.

Separators are classified into two-phase and three-phase separator. Two-phase separators are used to separate gas from the total liquid stream. Meanwhile, three-phase separators are used to separate gas from crude oil and water component.

Separators are designed in either horizontal, vertical, or spherical configuration. In this post, I want to share to you how to size two-phase horizontal separator.

Schematic of Two-Phase Horizontal Separator

Figure below is schematic drawing of two-phase horizontal separator.

Schematic of two-phase horizontal separator
Schematic of two-phase horizontal separator

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