Calculator › Brewery › Methodology
Compare heat loss before and after insulation, check the outer surface temperature, and convert the difference into annual energy and cost savings. The result depends on equipment dimensions, material properties and operating conditions.
Heat loss is the rate at which energy leaves the equipment. The calculator reports watts for the selected item or group; pipe results can also be expressed per metre. It compares bare and insulated conditions, then estimates the insulated surface temperature.
Annual savings are a second calculation. They combine the heat-loss difference with your operating hours, system efficiency, energy price and emission factor. A result for one metre of pipe is not a whole-site saving.
The three design modes answer different questions: Personnel protection finds thickness for a surface-temperature target; Condensation control compares the surface with the dew point; Freeze protection estimates when stagnant water reaches 0 °C.
The quick calculator uses one-dimensional thermal resistance. Heat passes through the insulation and then from its outer surface to the air. It holds the equipment surface at the entered process temperature.
q_bare = h × π × D × (T_hot − T_air)R_pipe = ln(r₂/r₁) / (2πλ) + 1 / (h × 2πr₂)q_insulated = (T_hot − T_air) / R_pipeT_surface = T_air + q_insulated / (h × 2πr₂)Here, q is heat loss per metre in W/m, r₁ is the bare radius and r₂ is the insulated radius, both in metres. Multiply q by pipe length to obtain total watts.
q_insulated = (T_hot − T_air) / (t/λ + 1/h)T_surface = T_air + q_insulated/hFor a flat surface, q is W/m². Multiply it by area to obtain watts. Thickness t is in metres and conductivity λ is in W/(m·K).
R_conduction = (1/r₁ − 1/r₂) / (4πλ)R_surface = 1 / (h × 4πr₂²)Vessel mode adds a cylindrical shell to one sphere, representing two hemispherical ends. This is an approximation, not the exact geometry of every dished head. The displayed surface temperature is the shell temperature.
The quick calculator fixes h at 10 W/(m²·K), combining external convection and radiation in one coefficient. It does not calculate wind speed or emissivity separately. This assumption is not a guarantee that losses are always overestimated or underestimated.
Brewery and industrial equipment studies calculate convection and radiation separately. Read the conditions on the selected study: air temperature, air movement, surface properties and equipment geometry can differ. Their results need not match the quick calculator.
For a source-backed product, the calculator interpolates its conductivity table and recalculates the outer surface until conductivity and temperature agree. The mean temperature is (hot-side temperature + calculated outer-surface temperature) / 2. Ambient air is used for the initial estimate, not as the final outer-surface temperature.
The conductivity shown at process temperature is a table lookup; it is not necessarily the effective conductivity used through the insulation. The full calculator shows both. A custom conductivity is held constant.
Product tables are not interchangeable: pipe sections, lamella mats and wired mats have their own values. The current input checks require both process temperature and solved mean temperature to fall within the selected table. A conductivity table's temperature range is not, by itself, the product's service-temperature rating.
Where a facing has its own temperature limit, compare that limit with the calculated outer-facing temperature, not automatically with the hot equipment temperature. Check the product's separate insulation and installation limits.
Personnel protection calculates the insulation thickness needed to reach your chosen outer-surface temperature. For example, a 45 °C design target means the calculated surface should be at or below 45 °C under the entered conditions.
A touch-safe assessment also considers the surface material, coating and expected contact time. ASTM C1055 relates contact-burn assessment to the surface system and exposure. ISO 13732-1 provides a method for assessing hot-surface contact; it does not prescribe one universal surface-temperature limit.
The tool calculates surface temperature and thickness, not skin temperature or burn injury. Select the target for the actual contact conditions, then check the installed surface. Heat bridges, fasteners and gaps can create local hot spots that the one-dimensional calculation does not represent.
Heat saved (kWh/year) = avoided heat loss (kW) × operating hoursInput energy saved (kWh/year) = heat saved / efficiencyCost saved per year = input energy saved × price per kWhEmissions avoided (tonnes/year) = input energy saved × factor (kg/kWh) / 1,000Efficiency, price and emission factor must refer to the same energy supply. For a fuel-fired boiler, the division by efficiency converts avoided heat loss into avoided fuel input. Do not apply a gas factor to purchased electricity or treat a boiler efficiency as a heat-pump COP.
The result is an estimate of avoided energy use, not automatically a verified reporting reduction. Accounting treatment depends on the energy source and reporting boundary. The calculator does not calculate carbon-credit revenue, a carbon tax or a CBAM bill.
Installed cost = entered cost per m² × modelled covered areaSimple payback (years) = installed cost / annual cost savingAnnual simple return (%) = annual cost saving / installed cost × 100Use a quotation or your own cost estimate. The calculator's starting values are not market prices. Simple payback holds operating hours and price constant; it does not include financing, discounting, future tariff changes or maintenance costs. A non-positive annual saving has no positive simple payback.
This arithmetic example uses a DN50 pipe with a 60.3 mm outside diameter, 150 °C hot surface, 20 °C air, 50 mm insulation and a custom constant λ of 0.050 W/(m·K). This is not the default product selection and does not describe a specific manufacturer's product.
| Quantity | Value | Unit |
|---|---|---|
| Bare heat loss | 246.27 | W |
| Insulated heat loss | 39.27 | W |
| Insulated surface temperature | 27.80 | °C |
| Annual input energy saved | 1,948.27 | kWh/year |
| Annual cost saved | 136.38 | EUR/year |
| Illustrative installed cost | 125.90 | EUR |
| Simple payback | 11.08 | months |
The annual calculation uses 8,000 hours, 85% efficiency, an illustrative price of €0.07/kWh and an illustrative installed cost of €250/m². Calculations retain full precision; table values are rounded. Changing any of those inputs changes the annual result.
| Input | Check before using the result |
|---|---|
| Equipment size | DN is a nominal size, not the measured outside diameter. Use Custom for another pipe diameter. |
| Temperature | Use the temperature at the hot-side boundary. A process-fluid temperature may differ from a measured casing temperature. |
| Material and thickness | Choose a product suitable for the temperature, shape, environment and installation. |
| Operating hours | Count hours at the stated conditions, not automatically every hour of the year. |
| Efficiency and tariff | Use the energy basis and price paid by the site. |
| Emission factor | Use a dated factor for the relevant energy supply and geography. |
| External coefficient | Fixed at 10 W/(m²·K) in the quick calculator; it is not a site measurement. |
| Mode | Input and calculation |
|---|---|
| Pipe | Outside diameter and length; cylindrical resistance. |
| Valve | DN and quantity; representative external area followed by a flat insulation model. Not equivalent metres of pipe. |
| Flat / walls / tanks | Exposed area; flat resistance. Useful for panels and locally flat surfaces. |
| Heat exchanger | External area per unit and quantity; flat resistance. This calculates heat escaping from the casing, not heat exchanged between process streams. |
| Vessel / tank | Diameter and straight shell length; cylinder plus two hemispherical ends. |
| Personnel protection | Pipe diameter and surface-temperature target; required thickness, rounded up to a standard size. |
| Condensation control | Cold-pipe and air temperature, humidity and diameter; thickness to keep the outer surface above the calculated dew point. |
| Freeze protection | Pipe size, insulation and water/air temperatures; cooling time for stagnant water to reach 0 °C, not time to freeze solid. |
A = 23.2D² + 1.37D + 0.0718D is the associated pipe outside diameter in metres; A is area per valve in m². The implemented relationship is attributed to ISO 12241:2022, Annex A.2.3, Table A.3, for manual flanged blocking valves in the DN15–DN200, PN16–PN25 range. It is not a measured contour for every valve type. Multiply by valve quantity; do not add flanges or pumps as extra valves.
For the modelled DN50 size, D = 0.0603 m and A = 0.238768 m² per valve. Compare irregular equipment with its actual dimensions before using the estimate for procurement.
Condensation mode uses the Magnus dew-point equation with constants 17.625 and 243.04 °C and a 0.5 °C design margin above dew point when insulation is required. The separate dew-point calculator lets you inspect the air calculation directly. Surface temperature alone does not establish vapour-barrier continuity or protection against corrosion.
Freeze mode uses a lumped cooling calculation for stationary water. It omits flow, heat tracing and the latent heat needed to freeze water. The quick model approximates the water radius from the selected outside diameter and omits pipe-wall heat capacity; it is not a pipe-schedule-specific freeze analysis.
Geometry is converted to metres internally. Conductivity is W/(m·K), heat-loss rate is W or kW, and annual energy is kWh or MWh. Temperature differences have the same numerical value in kelvin and degrees Celsius.
| Conversion | Relationship |
|---|---|
| kW to W | 1 kW = 1,000 W |
| MWh to kWh | 1 MWh = 1,000 kWh |
| W/m to Btu/(h·ft) | Multiply by approximately 1.040 |
| °C to °F | Multiply by 9/5, then add 32 |
The heat-loss modes assume steady operating conditions, uniform insulation and simplified geometry. They do not resolve supports, seams, thermal bridges, wet or damaged insulation, cycling duty or local air jets. Surface-temperature and material checks must be repeated for the actual installation.
Use a detailed study when airflow, radiation, complex geometry or variable operation materially affects the decision. No fixed accuracy percentage is claimed for every installation.
Calculation datasets and downloads: material properties, valve areas, dew-point tables, cost examples and quote templates, collected in one place.
Continue with Engineering Learning, pipe reference tables, the boiler-house worked example, HRSG heat-rate study or all calculators and guides.
Report a formula, source or result issue to contact@inzonex.co.uk. Include the page, equipment mode and input values so the result can be reproduced.
: aligned the equipment descriptions with the current quick model, distinguished surface-temperature targets from contact-burn assessment, and replaced the old combined pipe-and-valve example with an explicit one-metre calculation. No calculation-engine change in this documentation update.
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Compare the calculated heat loss with your equipment dimensions, operating conditions and access requirements before selecting an insulation system.
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