Compressor Volumetric Displacement
Compute the volumetric displacement of a reciprocating compressor, Vd = (π/4)·D²·L·n, the volume swept by the pistons, from the cylinder bore (D), the stroke (L) and the number of cylinders (n). It is the compressor's 'displacement' — the theoretical volume aspirated per revolution, which, multiplied by the speed and the volumetric efficiency, gives the actual flow. It defines the compressor capacity. Enter the bore, the stroke and the number of cylinders.
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Compressor volumetric displacement
The volumetric displacement (the compressor's 'swept volume') is the volume the pistons sweep per revolution: Vd = (π/4)·D²·L·n, a function of the cylinder bore (D), the piston stroke (L) and the number of cylinders (n). It is the theoretical volume drawn in on every turn of the shaft — and, multiplied by the rotational speed (rpm) and by the volumetric efficiency, it gives the actual volumetric flow of gas the compressor pumps. That actual flow, divided by the specific volume of the refrigerant at the suction, gives the mass flow rate, and from there the cooling capacity of the system. Displacement is therefore the fundamental geometric parameter that sizes a compressor: moving to a larger swept volume (or raising the speed, in variable-speed compressors) raises the capacity. In scroll, screw or centrifugal compressors the geometry differs, but the concept of volume displaced per unit time stays central. The π/4·D² term is simply the piston area; times the stroke, the volume of one cylinder; times the number of cylinders, the total. Enter the bore, the stroke and the number of cylinders.
Related Tools
Compressor Volumetric Efficiency
Compute a compressor's volumetric efficiency, ηv = (actual suction flow / volumetric displacement)·100%, the fraction of the piston-swept volume that actually pumps gas. Losses come from clearance volume (gas that re-expands), suction reheating and leakage. It drops as the compression ratio rises. It is a key indicator of compressor performance. Enter the actual suction flow and the volumetric displacement.
Refrigerant Mass Flow
Compute the refrigerant mass flow needed in a cycle, ṁ = refrigerating capacity / refrigerating effect, dividing the desired cooling load (kW) by the specific refrigerating effect (kJ/kg, the enthalpy absorbed per kilo at the evaporator). It is how much refrigerant must circulate per second to meet the demand — the basis for sizing the compressor, the piping and the system gas charge. Enter the refrigerating capacity and the refrigerating effect.
Cold Room Heat Load
Compute the product cooling heat load in a cold room, Q = m·cp·ΔT, from the product mass, its specific heat and the desired temperature change. It is the sensible-heat portion to remove to lower the product temperature — one of the components of the room's total load (which also includes wall transmission, infiltration, lighting, motors and people). It defines the refrigerating capacity needed. Enter the mass, the specific heat and the ΔT.
Superheat Degree
Compute the superheat of a refrigeration system, ΔT = T_suction − T_evaporation(saturation), how much hotter the refrigerant vapor is than its saturation temperature at the evaporator pressure. Proper superheat (typically 5–10 °C) ensures only vapor (no liquid) reaches the compressor, protecting it from liquid slugging. Too much superheat reduces capacity. It is controlled by the expansion valve. Enter the suction and saturated evaporation temperatures.
Compressor Work (Isentropic)
Compute the specific compression work in an ideal refrigeration cycle, W = h₂ − h₁, the enthalpy difference between the compressor outlet and inlet (isentropic compression, at constant entropy). It is the energy the compressor adds to the refrigerant per kilogram — the cycle's 'electricity bill'. Together with the refrigerating effect, it defines the COP (COP = refrigerating effect/work). Enter the outlet and inlet enthalpies.
Pile Bearing Capacity
Calculate a pile's ultimate bearing capacity, Q_ult = Q_p + Q_l, summing the point (tip) resistance Q_p (kN) and the side (skin friction) resistance Q_l (kN). The pile is the DEEP foundation element used when surface soil lacks capacity for the structure's loads — it transfers loads to deeper, stronger subsoil layers. This transfer occurs by TWO mechanisms acting at once: TIP resistance (the pile bears on a firm layer at its base, like a column, mobilizing the soil resistance under the tip) and SIDE resistance (friction and adhesion between the pile's lateral surface and surrounding soil, along its whole length). Their proportion defines the behavior: END-bearing piles (crossing soft soil to bear on rock or firm soil) work mainly by the tip; FLOATING or friction piles (driven in homogeneous soil, no firm layer) work mainly by side friction. The ultimate capacity, divided by a safety factor (typically 2), gives the design allowable load. Determining Q_p and Q_l — by theoretical formulas, SPT-based semi-empirical methods (Aoki-Velloso, Décourt-Quaresma) or load tests — is the central deep-foundation design calculation. Enter the tip resistance and the side resistance.
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