Abstract: A condensing heating module for heating a fluid and adapted for use with a radiant infrared burner. The heat exchanger within the module is spirally disposed about a central burner cavity and has a fluid flow passage of serpentine shape formed within its wall. The upper and lower surfaces of the module, together with the spiral wall of the heat exchanger, form a spiral condensing flue leading from the central burner cavity to an external flue. Those portions of the spiral heat exchanger wall and the module upper and lower surfaces which are exposed to direct radiation from the burner are formed of a corrosion resistant steel, while the remainder of the surfaces and wall are formed of carbon steel to which has been laminated a layer of polypropylene such that the polypropylene layer will be exposed to the flue gas and condensate environment and provide corrosion protection to the carbon steel.

Abstract: The brine tube of an ice thermal storage tank has a surface enhancement which provides nucleation sites for ice formation, and reduces the need to superchill the water. The tubing enhancement comprises a multiplicity of solid mineral particles distributed evenly over its surface. The particles have jagged, multi-faceted surfaces which adsorb air. When the brine in the tube cools the water to the freezing point, the adsorbed air coalesces into air bubbles that serve as nucleation sites. This permits freezing to initiate a temperature of about 31.5.degree. F.

Abstract: A fiberoptic probe for in situ sensing of liquid level, concentration and/or phase change contains the optical and electrical components as well as a reference fluid so that the components are at the temperature of the fluid to be monitored. A reference fiber is located in the reference fluid which is sealed in the probe so that volatile reference fluids can be used.

Abstract: Light in two different wavelengths, only one of which is attenuated by the presence of a substance to be tested for, is passed through a light path which includes a fluid path. The two wavelengths are equally attenuated by particulate contamination and all other conditions except for the presence of the tested for substance. A light path through a reference cell provides a reference for each wavelength. The presence of the tested for substance provides a differential attenuation which is indicative of the presence of the substance and the degree of differential attenuation is a measure of the concentration of the substance.