Refractories and Insulation Properties for CFD Simulation

CFD Input for Insulation Materials as Thermal Properties

• In CFD simulations involving heat transfer (conduction + convection + radiation), insulation layers require specific material properties. These properties determine heat loss, wall temperature, efficiency, and thermal stresses.

• Wall Material Definition

  You define a multi-layer wall:

  • Steel shell

  • Insulation (ceramic fiber, rock wool, etc.)

  B. Input Required

  • Temperature-dependent k(T)

  • ρ

  • Cp

  • Emissivity for radiation

  • Thickness

  C. Calculation Output Affected

  • Heat loss

  • Outer casing temperature

  • Furnace efficiency

  • Boiler energy balance

  • Thermal stresses (if coupled with FEA)

• Below are the essential properties and typical ranges used for common industrial insulation materials.

Insulation Materials – Thermal Properties

Density

Material	Density (kg/m³)
Ceramic fiber	64–160
Rock wool	50–200
Glass wool	10–60
Calcium silicate	200–300
Aerogel blanket	120–250

Thermal Conductivity (k)

Material	Typical k (W/m·K) @ 100°C	@ 300°C	Notes
Ceramic fiber blanket	0.05–0.10	0.10–0.18	Excellent high-temperature insulation (up to 1400°C)
Mineral wool / Rock wool	0.035–0.055	0.07–0.12	Common in boilers & ducts
Calcium silicate	0.06–0.08	0.10–0.14	Used in high-strength boiler casings
Glass wool	0.032–0.045	0.05–0.07	Building & low–medium temperature insulation
Perlite / Vermiculite	0.04–0.06	0.07–0.10	Moisture sensitive
Aerogel blanket	0.015–0.020	0.02–0.03	Best available insulation

Thermal Conductivity with Temperature

Material Type	Thermal Conductivity (W/m·K)	Max Temp (°C)	Used In
Dense Refractory Bricks	1.2 – 2.5	1500–1800	Furnace walls, boiler furnace bed
Insulating Fire Brick (IFB)	0.2 – 0.45	1100–1400	Furnace backup, heater walls
High-Alumina Castable	1.0 – 2.0	1500	Boilers, heaters, furnaces
Ceramic Fiber Blanket	0.12 – 0.20	1260–1400	Furnace lining, heater lining
Calcium Silicate	0.045 – 0.08	650–1000	Boilers, steam lines
Mineral Wool	0.035 – 0.045	750	Boiler & heater outer insulation

Maximum Service Temperature

Material	k (W/m·K)	Max Temp (°C)
Dense Fireclay Brick	1.3 – 1.8	1500
High Alumina Brick (70–90%)	1.8 – 2.5	1600–1750
Silicon Carbide Brick	4 – 6	1600
Insulating Fire Brick (IFB)	0.2 – 0.45	1100–1400
Castable Refractory	1.0 – 2.0	1400–1700
Ceramic Fiber Blanket	0.12 – 0.20	1260–1400
Calcium Silicate	0.045 – 0.08	650–1000
Mineral Wool / Rock Wool	0.035 – 0.045	750
Aerogel Blanket	0.016 – 0.020	650

Specific Heat Capacity (Cp)

Material	Cp (kJ/kg·K)
Ceramic fiber	1.05
Rock wool	0.80–1.2
Calcium silicate	0.75
Glass wool	0.80
Aerogel	0.70–1.00

Porosity

• ffects effective thermal conductivity

• Higher porosity → lower conduction

• Important if using homogeneous porous media modeling in CFD.

Typical porosity:

• Ceramic fiber: 85–95%

• Rock wool: 80–90%

• Aerogel: >90%

Furnace vs Boiler – Required Thermal Characteristics

Application Insulation and Refractories

Furnace, Boiler & Heater

Category	Equipment	Types Used	Description / Purpose
Refractories	Furnace (industrial, metallurgical, heat-treatment)	• Fireclay bricks • High-alumina bricks • Magnesia bricks • Silicon carbide bricks • Monolithic castables • Ramming mass • Ceramic refractory bricks (IFB for backup)	• Resist high temperature (1000–1800°C) • Withstand thermal shock • Resist slag/metal attack • Provide structural lining
	Boiler (power plant, industrial)	• Fireclay refractory bricks • High-alumina castables • Low-cement castables (LCC) • Insulating castables • Boiler refractory cement • Plastic refractory	• Furnace lining • Ash hopper lining • Burner throat / burner blocks • Slag-resistant materials
	Heater / Fired Heater (Refinery, petrochemical, API 560 heaters)	• High-alumina bricks (50–90%) • Ceramic fiber modules • Castable refractories (dense & insulating) • Anti-carburization refractory • Burner blocks (SiC)	• Protect tubes & shell from high heat flux • Reduce flame impingement damage • Maintain uniform temperature
Insulation	Furnace	• Ceramic fiber blanket / board / modules • Insulating fire bricks (IFB) • Perlite insulation • Calcium silicate boards	• Reduce heat loss through furnace walls • Lower fuel consumption • Backup insulation under refractories
	Boiler	• Mineral wool / rock wool • Calcium silicate insulation • Ceramic fiber blanket (high-temp zones) • Glass wool (low-temp areas)	• Shell insulation • Steam line insulation • Economizer & duct insulation • Prevent heat loss and condensation
	Heater / Fired Heater	• Ceramic fiber modules (1400°C) • Calcium silicate (outer insulation) • Mineral wool (duct & shell insulation) • Aerogel blankets (critical refinery lines)	• Maintain process temperature • Reduce skin temperature • Improve thermal efficiency • Protect metal structure

Refractories Application

Category	Types	Key Properties	Industrial Applications
Refractories	Acidic Refractories (Silica, Fireclay)	• Resist acidic slags • Good thermal shock resistance • High melting point	• Coke ovens • Glass tank regenerators • Ceramic kilns
	Basic Refractories (Magnesia, Dolomite)	• Resist basic slags & alkalis • High refractoriness • Good load-bearing strength	• Steel converters (BOF) • Cement rotary kilns • Steel ladles
	Neutral Refractories (Alumina, Chromite, Carbon/Graphite)	• Resist both acidic & basic corrosion • High strength • Oxidation resistance	• Electric arc furnaces • Induction furnaces • Foundry crucibles
	Special Refractories (Zirconia, Silicon Carbide, Carbides)	• Extremely high thermal resistance (≥2000°C) • Excellent abrasion resistance • High chemical resistance	• Aerospace & defence furnaces • Glass melting • High-temperature reactors
	Monolithic Refractories (Castables, Gunning mixes, Ramming mass)	• Easy installation • Joint-free lining • Good thermal shock resistance	• Boilers & incinerators • Petrochemical heaters • Furnace repair lining
	Insulating Refractories (Insulating bricks, IFB)	• Low thermal conductivity • Lightweight • Reduces heat loss	• Backup lining in kilns • Furnace outer walls • Heat recovery chambers

 

Insulation Materials for Industrial Applications

 

Category	Types	Key Properties	Industrial Applications
Insulation	Mineral Wool / Rock Wool	• Low thermal conductivity • Fire-resistant • Economical	• Boilers, turbines • Hot pipelines • Building insulation
	Ceramic Fiber (CF Blanket, Board, Modules)	• High-temperature capability (up to 1400°C) • Lightweight • Very low heat storage	• Furnaces, kilns, reformers • Glass/ceramic industry • Expansion joint & seals
	Calcium Silicate	• High compressive strength • Moisture resistant • Good for 650–1000°C	• Steam lines • Equipment insulation • Boilers & refinery heaters
	Perlite / Vermiculite	• Lightweight • Good insulation for medium temperatures • Fireproof	• Foundry insulation • Kiln backup lining • Cryogenic applications (special grade)
	Aerogel Insulation	• Extremely low thermal conductivity • Very thin profile • Water-resistant	• Refinery & petrochemical pipelines • Offshore platforms • Space/defense thermal shields
	PUF / PIR Foam	• Excellent low-temperature insulation • Lightweight • Closed-cell moisture resistance	• Cold storage • Refrigeration pipelines • LNG/LPG tanks
	NBR Rubber (Nitrile)	• Flexible • Good for chilled water lines • Moisture barrier	• HVAC systems • AC ducts & chillers • Pharma & food plants

 

Equipment	Refractories Used	Insulation Used
Furnace	High-alumina, fireclay, magnesia, SiC, castables, ramming mass	Ceramic fiber, IFB, perlite, calcium silicate
Boiler	Fireclay, castables, refractory cement, LCC, plastic refractory	Mineral wool, Ca-silicate, ceramic fiber (hot zones)
Heater (Refinery/Process Heater)	High-alumina bricks, ceramic modules, SiC burner blocks, insulating castables	Ceramic fiber modules, mineral wool, Ca-silicate, aerogel