Type a line (heat emission 350 kW combustion air 28 kg/s 4 fans) or fill in the fields: the line and the fields stay in step.
Enter the heat emission in kW and the combustion air of the engines and boilers in kg/s or m3/h, and the calculator works out the ventilation air by the ISO 8861 method: the combustion air qc, the air to remove the heat qh with a temperature rise of 12.5 K unless you enter another, and the total, the greater of qc + qh and 1.5 x qc. With the number of fans it gives the capacity of each, and fan capacities typed in the line (4 x 45000 m3/h) are checked against the total. The results come in m3/h, m3/s and kg/s, with the working step by step and a line you can copy or add to a request.
The engine maker’s project guide gives the air consumption and heat emission for each unit; add the generators, the boilers and the other equipment in the room. The calculator has no heat emission figures of its own and does not size ducts, dampers or fan pressure.
The air the engines and boilers burn, from their air consumption in the maker data: qc = m / rho, with rho = 1.13 kg/m3, the air density the method takes for its design air at 35 °C. The consumers add up: engines 24 kg/s and a boiler 4 kg/s make 28 kg/s, and 28 / 1.13 = 24.78 m3/s, or 89 204 m3/h. A flow given in m3/h is converted with the same density.
qh = phi / (rho x c x dT), with phi the heat emission in kW, rho = 1.13 kg/m3, c = 1.01 kJ/(kg K) and the temperature rise dT, 12.5 K in the method unless your specification sets another. For 350 kW: 1.13 x 1.01 x 12.5 = 14.27, and 350 / 14.27 = 24.53 m3/s, or 88 320 m3/h.
The total is the greater of qc + qh and 1.5 x qc: 24.78 + 24.53 = 49.31 m3/s against 1.5 x 24.78 = 37.17 m3/s, so 49.31 m3/s, or 177 524 m3/h, which is 55.72 kg/s. Shared by 4 fans, each moves 12.33 m3/s, or 44 381 m3/h.
| Quantity | Relation | Note |
|---|---|---|
| Combustion air | qc = m / rho | m the air consumption of the engines and boilers in kg/s from the maker data, added up |
| Air density | rho = 1.13 kg/m3 | for the design outside air of the method, 35 °C |
| Heat removal air | qh = phi / (rho x c x dT) | phi the heat emission in kW, added up over the units |
| Specific heat | c = 1.01 kJ/(kg K) | the specific heat capacity of the air |
| Temperature rise | dT = 12.5 K | the figure of the method, unless entered |
| Total | Q = max(qc + qh, 1.5 x qc) | the greater of the two |
| Per fan | Q / N | N fans sharing the total air |
| Units | 1 m3/s = 3600 m3/h | kg/s = m3/s x 1.13; 1 t/h = 1000 kg/h |
The heat removal air here is the gross figure, phi / (rho x c x dT): ISO 8861 itself takes a share of the combustion air off it, which this calculator does not do.
The relations and figures are those of ISO 8861 on the engine room ventilation of diesel-engined ships: the combustion air from the air consumption and an air density of 1.13 kg/m3, the heat removal air from the heat emission with c = 1.01 kJ/(kg K), a design temperature rise of 12.5 K with outside air at 35 °C, and the total as the greater of qc + qh and 1.5 x qc. They were checked against an engine maker’s product guide, a ventilation equipment maker’s technical article, two independent engineering calculator references and a discussion among engineers, each figure in at least two independent sources. The heat emission and the air consumption of each unit come from the engine maker’s project guide.
In three steps. The combustion air: qc = m / rho, the air consumption of the engines and boilers divided by the air density 1.13 kg/m3; 28 kg/s gives 24.78 m3/s, or 89 204 m3/h. The air to remove the heat: qh = phi / (rho x c x dT); 350 kW with c = 1.01 kJ/(kg K) and a rise of 12.5 K gives 350 / 14.27 = 24.53 m3/s, or 88 320 m3/h. The total, the greater of qc + qh and 1.5 x qc: 49.31 m3/s against 37.17 m3/s, so 49.31 m3/s, or 177 524 m3/h. Shared by 4 fans, each moves 44 381 m3/h.
When the air to remove the heat is less than half the combustion air: qc + qh is then below 1.5 x qc, and the total is 1.5 x qc. With 28 kg/s of combustion air (24.78 m3/s) and 100 kW of heat emission (7.01 m3/s), qc + qh = 31.79 m3/s, but 1.5 x qc = 37.17 m3/s, so the total is 37.17 m3/s, or 133 805 m3/h. The calculator shows which of the two sets the total.
12.5 K, the design figure of the method for the rise of the air through the engine room, unless you enter another, such as delta T 10 K. A smaller rise needs more air: 350 kW at 10 K needs 350 / (1.13 x 1.01 x 10) = 30.67 m3/s, against 24.53 m3/s at 12.5 K. A rise above 12.5 K is worked out too, with a note that the method takes 12.5 K at most.
The engine maker’s project guide gives the air consumption and heat emission for each unit, and the boiler and generator data give theirs. The calculator has no figures of its own: add up the heat emission of the engines, generators, boilers and the other equipment in the room you have figures for, and the combustion air of the engines and boilers that take their air from the room. A power in kW is not a heat emission, and the calculator says so when a kW figure stands next to a power word.
The fans share the total air: with 4 fans and 177 524 m3/h in all, each moves 44 381 m3/h, or 12.33 m3/s. The calculator does not choose reserve fans or a fan pressure; those follow your specification and the duct design. Fans already chosen can be checked: 4 x 45000 m3/h in the line, with the heat emission and the combustion air, is set against the total, and 180 000 m3/h is 101 % of 177 524 m3/h.
The heat emission in kW or MW, one figure or several that are added up; the combustion air in kg/s, kg/h, t/h, m3/s, m3/h or m3/min, one figure or several, such as the engines and a boiler; the temperature rise in K, 12.5 K unless entered; the number of fans; and the fans already chosen, as 4 x 45000 m3/h, to check them against the total. A flow in m3 is turned into kg/s with the air density 1.13 kg/m3. The heat removal air is the gross figure: ISO 8861 itself takes a share of the combustion air off it, which the calculator does not do.
The calculator gives the air the engine room needs. When parts for the engine room fans, their motors or the fire dampers are needed, send the line from the calculator with a photograph of the fan nameplate, and Vessel Core checks the details before an offer goes back.
