The Trane Company

Chester D Ware

Duane F Sanborn

John W Leary

Mark O Bergman

John L Holman

James T Lundblad

Donald S Fiegen

This invention is a method for pre-expanding a heat exchanger tube prior to its insertion into a tube sheet. A tubular mandrel having an elastic bladder sheath sealed at each end is inserted into the tube and positioned at the point where the tube is to be expanded. A die with an annular recess approximating the shape to which the tube is to be expanded is clamped around the outer surface of the tube, concentric to the mandrel. The elastic bladder is then pressurized with hydraulic fluid pumped through a passage in the mandrel, thereby deforming the tube outward so that it conforms to the recess in the die. A heat transfer enhancement treatment thereafter may be applied to the exterior of the tube between the expanded sections, without concern that it may crack off when the tube is installed in a tube sheet. In addition, the hydraulic pre-expansion process prevents or minimizes cracking of the tube which sometimes occurs when a tube is expanded to an equivalent diameter in a single operation.

Method for pre-expanding heat exchanger tube

A heat exchange surface having nucleate boiling cavities defined by subsurface cavities in combination with a thin porous coating. A preferred embodiment of the heat exchange surface includes a plurality of helical fins formed on the outer surface of a metallic tube, the tips of which are deformed by rolling to define gaps opening into fin cavities between adjacent fins. A porous open-celled coating flame-sprayed on the deformed portion of the fins substantially bridges these gaps, except at random open points caused by the inherent porosity of the coating. These openings in the porous coating in combination with the fin cavities provide nucleate boiling sites which promote efficient heat transfer for boiling a liquid.

Heat exchange surface with porous coating and subsurface cavities

An economizer is disclosed having a plurality of stages for flash cooling refrigerant liquid for use in a refrigeration system. The refrigerant liquid is cooled by evaporation of a portion of the liquid as it passes through throttling means into chambers of successively lower pressure. Sump means are provided to collect the refrigerant liquid flowing between the chambers. As the refrigerant enters each chamber, it is deflected by distribution means, thereby effecting more efficient separation of the flashed refrigerant vapor from the resulting liquid spray.

Multi-stage economizer

An air cooled centrifugal water chiller is disclosed which may be operable (1) under conditions of low outdoor ambient temperature, requiring flooding of the air cooled condenser in order to reduce its capacity and maintain proper system operation; or (2) in a heat recovery mode through the provision of a liquid cooled heat recovery condenser which thereby accommodates a portion of or all the condensing load, also requiring reduction in the capacity of the air cooled condenser through flooding. In order to provide sufficient refrigerant within the system to accommodate flooding under the conditions enumerated above, a refrigerant storage vessel is provided in communication with the shell of the evaporator of the system for receiving and storing excess liquid refrigerant during those operating conditions when it is not required in order to flood the air cooled condenser. An added feature lies in the provision of suitable service valves for isolating the air cooled condenser and the refrigerant storage vessel from the evaporator and centrifugal compressor such that liquid refrigerant from the evaporator may be pumped into the refrigerant storage vessel in order to allow servicing of the compressor or evaporator. In a preferred embodiment, the refrigerant storage vessel comprises an elongated pipe member connected at one end to the evaporator shell and extending therefrom along an axis generally parallel to the longitudinal extent of the air cooled condenser.

Air cooled centrifugal water chiller with refrigerant storage means

A refrigeration system is disclosed which includes evaporator means of the type for producing chilled liquid and wherein a compressor of the centrifugal type is provided for compressing refrigerant which has been vaporized in the evaporator means. Both air cooled and liquid cooled condenser means are connected in parallel flow relationship to the compressor, whereby the heat of condensation and compression may be rejected either to a source of ambient air or recovered through heat exchange with a source of liquid, whereby a heated liquid is produced for use as desired. Conduit means which are provided for passing condensed refrigerant from the air cooled and liquid cooled condenser means to the evaporator means include valve means for selectively varying the flow of condensed refrigerant from each, whereby the flow of condensed refrigerant from the air cooled condenser means may be reduced so as to cause at least partial flooding thereof and thereby reduce its capacity, while the flow of condensed refrigerant from said liquid cooled condenser means may be increased so as to increase the production of heated liquid. Control means are also disclosed for operating the aforesaid valve means in response to a sensed demand for heated liquid.

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La Crosse, WI, United States of America

Chester D Ware