US 4,676,305 AGranted

Microtube-strip heat exchanger

OwnerF. David Dotyinventor

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Abstract

A new approach to the theory of heat exchanger optimization is presented which shows the advantages of using low Reynolds and Nusselt numbers and low flow velocities along with a novel design, the microtube-strip (MTS) counterflow heat exchanger. The MTS exchanger in the preferred embodiment consists of a number of small modules connected in parallel. Each module typically contains eight rows of one hundred tubes, each of 0.8 mm outside diameter and 0.16 m length. The tubes are metallurgically bonded via the diffusion welding technique to rectangular header tube strips at each end. Caps suitable for manifolding are welded over the ends. Cages are provided to cause the shell-side fluid to flow in counterflow fashion over substantially all of the tube length, and suitable manifolds are provided to connect the modules in parallel. This design results in the highest power densities of any known design for single phase exchangers. Although the MTS exchanger of the present invention is specifically optimized for applications not involving phase changes in the working fluid, the essential concepts and features of this invention can also be advantageously used in applications involving change of phase.

Claims16

Dependent claims

A gas-gas laminar-flow heat exchanger module which comprises:

a plurality of heat transfer augmentation-free corrosion resistant, precision, hardened, metallic tubes arrayed in at least four parallel disposed planar rows of at least forty tubes per row;
a first rectangular header strip interference press fit and diffusion welded to one end of each of said tubes;
a second rectangular header strip interference press fit and diffusion welded to the other end of each of said tubes;
first manifold means metallurgically connected to said first rectangular header strip for defining a gas inlet flow path into said one end of each of said tubes;
second manifold means metallurgically connected to said second rectangular header strip for defining a gas outlet flow path from said other end of each of said tubes;
means disposed externally of said tubes for defining a counterflow flow-path of heat exchanger gas over substantially the entire length of the external surfaces of each of said tubes from within the vicinity of said other end of each of said tubes to within the vicinity of said one end of each of said tubes;
each of said tubes having an outside diameter of less than 3 mm;
each of said tubes having a length which is sufficient to allow for fully developed laminar flow and which is less than 300 times said outside diameter of each of said tubes;
and
said plurality of tubes within each of said rows being laterally spaced by a center-to-center distance of from 1.3 to 2.8 times the outside diameter of each of said tubes.

7 more elements

Dependencies are inferred from the claim text.