Power plants – Motive fluid energized by externally applied heat – Process of power production or system operation
Reexamination Certificate
1999-11-15
2001-01-30
Nguyen, Hoang (Department: 3748)
Power plants
Motive fluid energized by externally applied heat
Process of power production or system operation
C060S682000
Reexamination Certificate
active
06178750
ABSTRACT:
Malone has described a method (Journal of The Royal Society of Arts, Jun. 12, 1931, pp. 679-703) wherein heat is abstracted from a heated working medium for its further utilization in the production of mechanical energy. To this end Malone employs an apparatus (also described in the thermodynamics atlas, Longman Group Ltd., pp 78 and 90, 1972) comprising a first and a second vertical elongated chamber, which chambers are continuously heated at the base. The apparatus, and consequently also each chamber, is filled with water as the working medium, which expands in the chambers as a result of heating. The first vertical chamber is in communication with a first drive chamber, the second vertical chamber communicates with a second drive chamber. The first and second drive chambers are placed in each other'extensions and at their facing sides they are sealed by means of a movable double piston. When the double piston is in a first extreme position, the first drive chamber's volume is at a maximum, while that of the second drive chamber is at a minimum, and vice versa. Through the expansion of the working medium in the first vertical chamber the first drive chamber is being filled, thereby moving the double piston. This drives a crankshaft which transmits the mechanical energy produced. Moving the rod-like elements in vertical direction does not alter the volume available for the working medium in an elongated chamber. When the one elongated element is in the highest position, the other elongated element is in the lowest position. Further, an elongated element is 90° out-of-phase in relation to the position of the double piston. When the working medium in the elongated chamber expands, it moves upward along the elongated element, filling the drive chamber with which the elongated chamber is in communication. The crankshaft rotates the elongated element to a lower position. This results in there being less working medium in the heated part of the elongated chamber and the working medium cooling off in the higher part of the elongated chamber. Due to cooling, the working medium contracts and the drive chamber which is in communication with the elongated chamber, empties. This, too, contributes to the driving of the double piston. The other elongated chamber is 180° out-of-phase, filling at the same moment the other drive chamber, which drives the crankshaft. Between the part of the elongated chamber that is being heated and the part that is being cooled, a heat exchanger is provided. When the hot working medium rises it gives out heat to the heat exchanger. When the working medium drops, it reabsorbs this heat. Therefore, when the apparatus is in operation, the lower part of the heat exchanger is hot, while the upper part is cold. The advantage of this kind of heat exchange is that there is little heat loss to the cooling medium, with the result that the conversion of heat into mechanical energy is highly efficient. Malone used water as working medium, while the apparatus operated at a working-medium pressure of approximately 700 atm. At a hot/cold temperature difference of 250° C. his apparatuses yielded an output of 23 percent.
The disadvantage of this method is that the working medium in the expansion and working phase has to pass a cold heat exchanger to which it gives out heat. This means that during the production of mechanical energy, the working medium contracts, and this reduces efficiency. Conversely, during its mechanical energy-producing contraction phase, the working medium absorbs heat causing it to expand, so that in this phase of the method, too, efficiency is reduced. Admittedly, little energy is lost, but the transport of heat to and fro is not useful. The rod-like elements also have a heat exchanging effect. As they move in relation to the heat exchanger, their temperature at a particular height does not correspond with that of the heat exchanger. This limits the efficiency of heat recovery. For a particular output power to be supplied to the (crank)shaft, the apparatus is large and demands a heavy construction.
The present invention allows the heat exchanger to be maintained, at least substantially, at the same temperature and avoids that the working medium undergoes a heat exchange which would counteract the production of mechanical energy.
According to a favourable embodiment the liquid is conducted into the second part in counter current to a cooling medium, yielding heated cooling medium, and the heat of the thus heated cooling medium is conducted in counter current with the working medium into the first part for the production of mechanical energy.
By using such a method it is possible to employ heat exchangers of a simple and consequently cheap construction.
According to a preferred embodiment of the method according to the invention the liquid used is a liquid whose expansion coefficient in a working range is at least 0.02%/°C., preferably at least 0.05%/°C. and most preferably at least 0.7%/°C.
A liquid with a high expansion coefficient promotes the effective conversion of heat into mechanical energy, in particular the generation of electrical energy.
Preferably, the working range lies between 15° C. and 100° C.
Thanks to its high efficiency, the method according to the invention is very suitable for using heat sources of a relatively low temperature.
In such a case the liquid used is preferably a paraffine-comprising liquid.
Paraffine-comprising liquids such as paraffine and paraffinic solutions in, for example, hydrocarbonic solvents, exhibit a remarkably high expansion coefficient at relatively low temperatures, which makes them very suitable for the production of mechanical energy by means of the method according to the invention.
In order to reduce in a suitable apparatus the energy losses incurred by internal resistance, a liquid is employed as the paraffine-containing liquid, which comprises an additive capable of lowering the internal resistance.
For the convenient reduction of flow resistance a substance such as Petrolad (B.R.B., Ittervoort, the Netherlands) is added, for example, in a ratio of 1:10,000. To reduce the friction between moving parts, for example 1-4% of a molecular lubricant, teflon or molybdenum sulphide may be added, the latter two to be dispersed in the working medium in the form of granules with an average size of, for instance, 3 &mgr;m.
If one wishes to employ for the production of energy some available heat source, the working range may very advantageously be adapted by using as the paraffin-comprising liquid a paraffinic liquid having a working range that has been shifted to a lower temperature through dilution.
In another embodiment according to the invention the working medium, in the part to be heated, is heated in counter current with a heat source.
In this manner the thermal energy present in the heat source is optimally utilized.
The invention also relates to an apparatus suitable for the conversion of thermal energy into mechanical energy according to a method in accordance with one of the claims
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, which apparatus comprises a part to be heated and a part to be cooled, which parts form a closed circulation system for the working medium, wherein during operation the working medium is able to flow from the part to be heated to the part to be cooled, and the apparatus is further provided with a shaft to be driven by the working medium and a heat exchanger for the recovery of thermal energy that has not been converted into mechanical energy, wherein
the part to be heated has a first inlet opening for cold working medium and a first outlet opening for heated working medium,
the part to be cooled has a second inlet opening for heated working medium and a second outlet opening for cold working medium,
via a first switch valve in a first position the first outlet opening is in communication with a first storage chamber for heated working medium and in a second position with a second storage chamber for heated working medium, and the second inlet opening is in the second position in communication with the fi
van der Werff Jeichienus Adriaan
van der Werff Johannes Jeichienus
Cyclo Dynamics B.V.
Kinney & Lange , P.A.
Nguyen Hoang
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