Material Selection for Heat Insulation

Material Selection for Heat Insulation

The selection of insulating material is depend on the properties of material such as thermal resistance, heat capacity, density and thermal conductivity. The purpose of insulation is to ensure is to avoid the heat from radiating away and also to improve the working environment condition. Generally, insulation idea is approach by the heat capacity of material and the existing of pocket air , air has lower thermal conductivity than solid and the stagnant air has low convection air coefficient in the absence of bulk movement flow of fluid. 

(1) Mineral Rock

Form by spun molten glass, stone, ceramic fiber into fiber structure.

(2) Calcium Silicate

Form by react polyol (alcohol with two or more hydroxyl group) with polymeric isocyanate.

(3) Fiber Glass

Form by finely woven silicon, glass powder and tiny shards of glass spun into microfibers.

(4) Polyurethane Foam

Form by react methylene diphenyldiisocyanate (MDI) and polymeric methylene diphenyldiisocyanate (pMDI) , foam is produced when is expend on contact

(5) Cellulose

Form by shredded recycled paper through a loosed filled processes)

Insulating material	Thermal resistance(K/W)	Specific Heat capacity(kJ/kg. K)	Thermal conductivity(W/m. K)	Density (kg/m3)	Temperature range(°C)
Mineral Rock wool	3.7-4.3	0.7-0.8	0.01-0.04	100-150	0 ~750
Calcium silicate	1.0-1.4	0.7-1.05	0.07-0.17	250-600	0 ~1200
Fiber glass	2.0-3.3	0.7-0.85	0.015-0.025	20-50	-18 ~1400
Polyurethane Foam	3.8-4.0	0.14-0.17	0.02-0.04	30-50	0 ~1150
Cellulose	3.0-3.6	0.18-0.25	0.35-0.04	30-80	0 ~1350

 *The thermal conductivity is taken from average value of product in market, while the R value per inch is taken from specific product produce by US company.

The thermal conductivity of product is direct factor in determine the heat transfer through the surface, in order to reduce the total coefficient of heat transmission,as the value of thermal conductivity increase, the heat flow through the surface is inversely proportional, and the value of thermal resistance (R-value) is inversely proportional to the thermal conductivity, thus the larger the R value ,the lesser the heat can pass through. From the table 1 can seen that the mineral rock and polyurethane foam has the lowest thermal conductivity and also higher R-value, so it has better insulation than other.

But the Specific Heat Capacity of a material for polyurethane foam is lowest among five insulating material, while the calcium silicate has higher value of specific heat capacity among five material, specific heat capacity is the amount of heat needed to raise the temperature of 1 kg of the material by 1 K (or by 1°C) . A good insulator has a higher Specific Heat Capacity because it takes time to absorb more heat before it actually heats up (temperature rising) to transfer the heat. High Specific Heat Capacity is a feature of materials providing thermal buffering (Decrement Delay, 2015).

While seen from density properties of material ,calcium silicate having obviously density among all 250-600, and mineral rock wool has second highest of density in average value of 100-150, while the polyeuthane  foam and fiberglass having lowest density, the higher density insulating material can  maximizes the overall weight and is an aspect of 'low' thermal diffusivity and 'high' thermal mass. (Foundrymagcom, 2017)

From temperature range ,the calcium silicate also having higher temperature which up to 1200°C, temperature is fairly important factor in determine the selection of product before the failure occur , palm oil heat recovery sometimes can goes up to 1000°C ,other insulation material especially polyurethane foam which may melt or change shape beyond its temperature range. (Scribdcom, 2017)

Generally ,it can be seen that the calcium silicate is most suitable in insulation of heat exchanger for recovery of palm oil, which has higher heat capacity ,density and temperature limit.

The operating requirement for the calcium silicate is the surrounding air must be dry, the moisture condition can cause shape deformation. In addition, calcium silicate should be far away from UV radiation (sunlight) to avoid degradation of calcium silicate. Other than that, the surface must avoid any direct contact by mechanical means to avoid the shave off of the calcium silicate which can cause lung cancer (Foundrymagcom, 2017).

Calcium Silicate insulation is recommended for use in the petrochemical, power generation and process industries where piping and equipment operating at high temperature. The advantage of calcium silicate is it is light weight, reliable and durable ,no need any addition bone to acts as support, and it is also environment friendly as it free from asbestos, mercury and lead. In addition, it doesn’t irritant smoke when operating at high temperature. In addition , it able to resists fire for about 90-120 min and any chemical corrosion. It also able protects against damage by lagging due to structural strength and thermal shock resistance (Newsjmcom, 2017).

While the disadvantage of calcium silicate is it will gain weight when absorb moisture from surrounding and cause fungus growth and is difficult in installation as care must be taken to avoid dust fall as the calcium silicate is fragile ,the most interesting is it is cost efficient as it is no expensive and no need special maintenance, and is easier to remove when maintenance is carry on heat exchanger (Blogspotmy, 2017).