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Variable refrigerant flow (VRF), also known as variable refrigerant volume (VRV), is an HVAC technology invented in Japan in 1982. Like ductless minisplits VRFs use refrigerant as the cooling and heating medium. This refrigerant is conditioned by a single outdoor condensing unit, and is circulated within the building to multiple fan-coil units (FCUs).

All piping, valves, fittings and other components for use in all non-flammable medical gas systems must be thoroughly cleaned by the manufacturer to remove oil, grease and other readily oxidizable materials as if they were being prepared for oxygen service. Use particular care in storage and handling. Such material must be capped or plugged to prevent recontamination before final assembly. Just prior to final assembly, the material must be examined internally for contamination.

Designing a copper tube water supply system is a matter of determining the minimum tube size for each part of the total system by balancing the interrelationships of six primary design considerations:

  • Available main pressure;
  • Pressure required at individual fixtures;
  • Static pressure losses due to height;
  • Water demand (gallons pter minute) in the total system and in each of its parts;
  • Pressure losses due to the friction of water flow in the system;
  • Velcity limitations based on noise and erosion.

A table indicates copper pipe's types, standards and applications.

Thermal conductivity (k, also denoted as λ or κ) is a measure of a material's ability to conduct heat. Heat transfer across materials of high thermal conductivity occurs at a higher rate than across materials of low thermal conductivity. In the International System of Units (SI), thermal conductivity is measured in watts per meter Kelvin (W/(m•K)). In the Imperial System of Measurement (British Imperial, or Imperial units), thermal conductivity is measured in Btu/(hr•ft⋅F).

Strong, long lasting, copper tube is the leading choice of modern contractors for plubing, heating and cooling installations in all kinds of residential and commercial buildings. The primary reasons for this are;

Copper is economical.

The combination of easy handling, forming and joining permits savings in installation time, material and overall costs. Long-term performance and reliability mean fewer callbacks, and that makes copper the ideal, cost-effective tubing material.

Copper is lightweight.

This table is in Chinese version, compares the datas of copper straight pipe and coil standards.

You could tell the differences between  international standards includes: GB/T 17791-1999, ASTM B68, ASTM B75, ASTM B280, ASTM B743, JIS H3300.

This specification covers the requirements for seamless UNS C10200, C12000, or C12200 copper alloy tubes used for connection, repairs, or alternations of field air conditioning or refrigeration units. Materials in the form of billets, bars, or tubes should be used to produce a homogeneous uniform wrought structure by either hot or cold working. Each tube should be cold drawn to the finished size and wall thickness. Coiled lengths with soft annealed tempers should be bright annealed after coiling then dehydrated and either capped, plugged, crimped, or otherwise closed at both ends. Straight lengths with hard drawn tempers should be cleaned and either capped, plugged, or otherwise closed at both ends. The grain sizes, tensile properties, and eddy-current and cleanness test results should conform to the values listed herein.

This European Standard was approved by CEN on 23 March 2006.

EN 1057:2006 specifies the requirements, sampling, test methods and conditions of delivery for seamless round copper tubes.

It is applicable to tubes having an outside diameter from 6mm up to and including 267mm for:

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