Photography – Fluid-treating apparatus – Heating – cooling – or temperature detecting
Reexamination Certificate
1999-03-16
2001-02-13
Rutledge, D. (Department: 2851)
Photography
Fluid-treating apparatus
Heating, cooling, or temperature detecting
C396S626000
Reexamination Certificate
active
06186681
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for treating aqueous fluids, such as photographic processing solutions, to control biogrowth. Thus, this invention provides a method for sterilizing such solutions. The invention also relates to a heat transfer apparatus that can be used in the noted method. This invention has utility in the photographic, chemical food processing and health industries.
BACKGROUND OF THE INVENTION
In various industries, including the photoprocessing industry, aqueous solutions are susceptible to biogrowth under certain conditions. Biogrowth, that is growth of bacteria and/or fungus, can be a problem for many reasons of health, safety and quality in the food, chemical, photographic and health industries.
Attempts to reduce or eliminate the problem of biogrowth have included discharging solutions to the environment followed by cleaning of machines and processing tanks and equipment, adding chemical biocides, radiation treatment of solutions, and various filtration techniques. Because of biogrowth in the photographic industry, the useful life of photoprocessing solutions has been unnecessarily reduced, photoprocessing equipment has been cleaned too frequently, and fresh solutions are needed at additional labor and chemical costs.
Each of the known methods for reducing biogrowth has inherent disadvantages. For example, the use of chemical biocides gives uncertain results and requires the handling of expensive chemicals that are often hazardous. Frequently discharging solutions to the environment has obvious problems and is increasingly regulated in many countries. Ultraviolet radiation is not efficient for treating colored solutions. The addition of heavy metals such as silver and copper to control biogrowth is often in conflict with governmental regulations for discharge of effluent. The addition of silver to photographic processing solutions causes the formation of silver complexes that fail to inhibit microbial growth. Filters can be clogged quickly and require frequent replacement or cleaning, and can become microbial breeding grounds.
The use of heat to control biogrowth is well known, particularly in the food industry. Of the methods used to provide heat (including boiling and autoclaving), pasteurization involves exposure to high temperatures for a relatively brief time. In bulk pasteurization, the process typically involves heating a fluid to about 65° C. for 30 minutes. In flash pasteurization, the fluid is heated to a higher temperature (over 70° C.) for much less time (for example, 15 seconds).
Thermoelectric refrigeration is a known technology [
CRC Handbook of Thermoelectrics,
Rowe (Ed.), Inc. 1995, pp. 597-676]. This technique involves passing a current through one or more pairs of n- and p-type semiconductor materials, providing both hot and cold sides that can be contacted with fluids to be treated. At the cold side, direct current passes from the n- to the p-type semiconductor material and heat is absorbed from the environment (in this case, the treated fluid). The adsorbed heat is transferred through the semiconductor materials by electron transport to the other side of the junction and liberated as electrons return to a lower energy level in the p-type material. This phenomenon is called the Peltier effect, and devices used in this manner are often called Peltier heat transfer devices. More than one pair of semiconductors are usually assembled together to form single or multistage thermoelectric modules.
In the operation of such modules as heat transfer devices, usually one fluid is heated while another is cooled (see for example, see U.S. Pat. No. 3,506,543 of Hayes et al and U.S. Pat. No. 5,027,145 of Samuels). Alternatively, such heat transfer devices can be used to provide heat for evaporation of one fluid and condensation of another, as described for example in U.S. Pat. No. 4,316,774 (Trusch).
In the noted Samuels patent, a Peltier heat device is used in conjunction with photographic film processors that utilize both a developer bath and a water wash bath. During use of the heat device, the developer is cooled while the water wash is heated.
There is a need to provide an improved means for inhibiting biogrowth in various aqueous fluids, especially photographic processing solutions, in which the same fluid is treated on both sides of the Peltier heat transfer device to provide adding efficiencies.
SUMMARY OF THE INVENTION
The problems noted with current methods of preventing biogrowth have been overcome using a thermoelectric Peltier heat transfer device having a cold side and a hot side that are in direct fluid flow communication so that the same fluid is treated on both the cold and hot sides of the heat transfer device.
This heat transfer device can be used in a method for treating a fluid comprising the steps of:
A) contacting a fluid with the hot side of the heat transfer device for a residence time sufficient for flash pasteurization of the fluid without any volume loss of the fluid, and
B) directly contacting solely the flash pasteurized fluid with the cold side of the heat transfer device to rapidly cool the flash pasteurized fluid.
This invention also provides a method for treating a photographic processing solution in a thermoelectric Peltier heat transfer device having a cold side and a hot side that are in direct fluid flow communication so that the same photographic processing solution is treated on both the cold and hot sides of the heat transfer device, comprising the steps of:
A) contacting a photographic processing solution with the hot side of the heat transfer device for a residence time sufficient for flash pasteurization of the photographic processing solution without any volume loss of the flash pasteurized photographic processing solution, and
B) directly contacting solely the flash pasteurized photographic processing solution with the cold side of the heat transfer device to rapidly cool the flash pasteurized photographic processing solution.
The device and method of this invention can be used to sterilize the treated fluid on one side of the heat transfer device (the hot side) by flash pasteurization, and then rapidly cool the treated fluid to an appropriate temperature using the cold side of the same device. Thus, the same fluid is contacted simultaneously with both hot and cold sides of the thermoelectric Peltier heat transfer device. Thus, the hot and cold sides are connected in a suitable fashion to provide “direct” fluid flow communication without intervening tanks, compartments or treatments. In other words, the treated fluid passes directly from the hot side of the heat transfer device to the cold side.
Flash pasteurization on the hot side of the device kills any microorganisms and fungi present in the fluid. When the invention is used in photographic processing, the treated solution can be returned to the processing tank without substantial change in temperature within a few seconds of treatment. Substantially no fluid is lost in the method because little evaporation occurs during flash pasteurization in the closed system of the invention. Importantly, the heat transfer device and method of this invention allow pasteurization without interruption of photoprocessing or other chemical processes in which the treated fluids are used. This advantage is usually transparent to the actual users since the fluid leaves and re-enters a processing tank (or other fluid reservoir) at nearly the same temperature, and the device and fluid connections can be hidden from view, thereby providing additional safety features.
In the use of “hot side” and “cold side” of the device of this invention, we mean that the hot side of the device is a source of heat for heating up the treated fluid. Thus, the fluid becomes a heat sink on the hot side of the device. Conversely, the cold side of the device refers to a side that absorbs heat from the treated fluid, thereby cooling the fluid. Thus, the fluid is a heat source for the cold side.
Other advantages of the invention will become apparent upo
Christ Charles S.
Davis Daniel C.
Szembrot Albert R.
Eastman Kodak Company
Rutledge D.
Tucker James L.
LandOfFree
Method and apparatus for pasteurizing fluids does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for pasteurizing fluids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for pasteurizing fluids will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2581013