Compression Ratio (Refrigeration)
Compute a refrigeration system's compression ratio, rc = Pcondensation/Pevaporation, the ratio of the compressor's absolute discharge to suction pressures. High ratios (above ~10) lower volumetric efficiency, raise the discharge temperature (risking oil and refrigerant degradation) and may require two-stage compression — common at low temperatures and in cryogenics. Enter the condensation and evaporation pressures (absolute).
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Razão de compressão (refrigeração)
A razão de compressão rc = Pcondensação/Pevaporação (pressões absolutas) é um dos números que mais condicionam o projeto e a operação de um sistema de refrigeração. Ela sobe quando se quer evaporar a temperaturas muito baixas (pressão de evaporação cai) ou condensar a temperaturas altas (dias quentes, condensador sujo). E razões altas trazem três problemas em cascata: a eficiência volumétrica do compressor cai (mais reexpansão do espaço morto), reduzindo a capacidade; a temperatura de descarga dispara, podendo carbonizar o óleo lubrificante e decompor o refrigerante (formando ácidos que corroem o sistema); e o COP piora, gastando mais energia. Acima de uma razão de ~8 a 10, a engenharia recorre à compressão em duplo (ou múltiplo) estágio, com resfriamento intermediário entre os estágios — padrão em câmaras de congelados, freezers industriais e, levado ao extremo, na criogenia e liquefação de gases, onde cascatas de vários refrigerantes diferentes são encadeadas. Informe as pressões de condensação e de evaporação absolutas.
Related Tools
Screw Compression Ratio
Calculate an extrusion screw's compression ratio, CR = H_feed ÷ H_metering, from the channel depth in the feed zone H_feed and the metering zone H_metering. An extrusion screw has three zones: feed (deep channel, receiving solid pellets), compression (transition, channel tapering) and metering (shallow channel, homogenizing and pumping the melt). The compression ratio is how much the channel narrows from inlet to outlet — typically 2:1 to 4:1. This compression is essential: by reducing channel volume it compacts the pellets, expels trapped air (which must vent back through the feed, not go forward) and generates the shear and pressure that melt the polymer by viscous heating (plus barrel heat). The right ratio depends on the polymer: materials melting with large volume reduction and amorphous ones need different ratios from semicrystalline. A wrong ratio causes incomplete melting, air pumping, flow instability (surging) or degradation. It is one of the parameters that define whether a screw suits a given material. Enter the feed and metering channel depths.
Crushing Reduction Ratio
Calculate the reduction ratio of a crusher or mill, RR = F ÷ P, dividing the feed size F by the product size P (usually F₈₀/P₈₀ or crusher openings). The dimensionless result shows how many times the material was reduced in size in one stage. Each equipment type has a typical reduction ratio range: jaw crushers 4-7, cone crushers 5-8, ball mills up to 100 or more. Since each stage has a limited ratio, reducing large blocks to fine powder requires several stages in series, whose product of ratios gives the total reduction. Enter the feed and product sizes.
Gear Base Diameter
Calculate the base circle diameter of an involute gear, d_b = d·cos(φ), from the pitch diameter d (mm) and the pressure angle φ (degrees). The base circle is the circle from which the INVOLUTE tooth profile is generated — the standard profile of modern gears. The involute is the curve traced by the tip of a string unwinding from a cylinder: that cylinder is exactly the base circle. The entire active tooth profile (the part that actually transmits force) is ABOVE the base circle; below it there is no involute profile. The base diameter is fundamental in gear geometry because it defines the involute profile and, with it, key properties: the LINE OF ACTION (the line tangent to both base circles of the mesh, along which tooth contact travels, always in the same direction — why involute gears transmit uniform motion), the base pitch and the contact ratio. The relation d_b = d·cos(φ) shows that the pressure angle is the angle between the line of action and the tangent to the pitch circles. It is an essential parameter in designing and manufacturing (generating) involute gears. Enter the pitch diameter and the pressure angle.
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