Copper finned tubes

Radiators eure composed of copper fins, tubes which until recently were soldered with a lead-tin solder. Currently, soldering with zinc and brazing are being studied. 

This is the exchanger where heat flows from the room return or mixed air to cold refrigerant or to chilled water. It is an arrangement of finned tubes normally of aluminum fins on copper tubes, but copper fins can be specified for corrosive atmosphere. Performance characteristics are controlled by fin and tube spacing. If the room rh is high, dehumidification may be brought into use by operating the coil or one of a number of parallel coils at a low temperature. If the room s sensible heat load is low reheat must be allowed to operate at the same time. 

Materials of construction are aluminium fins on stainless steel tube for ammonia, or aluminium or copper fins on aluminium or copper tube for the halocarbons. Aluminium tube is not yet common, but its use is expected to increase. 

Copper fins with a thickness of 1.0 mm are installed on a 2.5-cm-diameter tube. The length of each fin is 12 mm. The tube temperature is 250°C and the fins are exposed to air at 30°C with a convection heat-transfer coefficient of 120 W/m2 °C. Calculate the heat lost by each fin. 

Internal Flow. Internally finned circular tubes are commercially available in aluminum and copper (or copper alloys). For laminar flow, the following correlations are available [113] Spiral-Fin Tubes. 

The materials commonly used for finned tube absorbers are copper, aluminum, or steel [44]. Copper is rather expensive for dryer collectors. Aluminum gives a long operation... 

Sample Specifications % in. (1.9 cm) outside diameter externally finned, copper tubes... 

Figure 14.6 Material defect, perhaps a lap or seam, on the external surface of a finned copper tube.

The diameter and materials, specified for the tubes and fins, depend on system requirements. The fins are commonly made from aluminum or copper, but may be fabricated of stainless or carbon steel. Tubes are generally copper, but can be made from almost any material, and they range in size from 5/8- to 1-in. outer diameter. The design of the air-cooled exchanger is such, that individual coils can be removed independently for easy cleaning and maintenance. There are several common design configurations that are commercially available. Each is briefly described below. 

Tubes are copper 1-in. nominal O.D. X 14 BWG (0.083-in. thick at finned section) X 19 fins/in. Wolverine Trufin (standard tube (unfinned) wall thickness = 0.095 in.). Finned surface area/ft length = 0.678 fti/ft. Plain tubes are 0.5463 ftVft. 

Tubes, Figure 10-183A and 10-183B, are usually finned with copper, aluminum, steel, or a duplex combination of steel inside with copper or aluminum fins outside. Other combinations are used to suit the service with the ratio of... 

Construction materials will be the same as for air-cooled condensers. Aluminium fins on copper tube are the most common for the halocarbons, with stainless steel or aluminium tube for ammonia. Frost or condensed water will form on the fin surface and must be drained away. To permit this, fins will be vertical and the air flow horizontal, with a drain tray provided under. 

Both types of boiler systems may incorporate finned copper heating coils, which are located above the furnace and gas-pass tubes (smoke tubes or fire tubes) and provide for indirect heating of domestic HW. Where coils are fitted and the boilers are only fired during winter months, domestic HW heating usually is provided via gas heaters for the summer. 

The fin surface area will not be as effective as the bare tube surface, as the heat has to be conducted along the fin. This is allowed for in design by the use of a fin effectiveness, or fin efficiency, factor. The basic equations describing heat transfer from a fin are derived in Volume 1, Chapter 9 see also Kern (1950). The fin effectiveness is a function of the fin dimensions and the thermal conductivity of the fin material. Fins are therefore usually made from metals with a high thermal conductivity for copper and aluminium the effectiveness will typically be between 0.9 to 0.95. 

The tube pattern is triangular, the fin material is aluminum, and the tube material is copper. 

When Eqs. 14.88, 14.89, 14.90, and 14.91 were compared to existing data for finned copper tubes, good agreement was found for B = 0.143 and B, = 2.96. Briggs and Rose [96] extended this model to low conductivity materials by including conduction effects in the fins. 

A1 walked over and looked out. Buck Rogers s very own rocketship was sitting on the rock shelf below him. It was a beautiful scarlet torpedo with yellow fins sprouting from the sides, and a cluster of copper rocket engine tubes at the rear. 

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