The present invention relates to a reciprocating, two-stroke mechanical freezer with one piston moving in with a sinusoidal motion and one or more displacer pistons moving in non-sinusoidal motion so that it obtains cooled compression.
The Mechanical Freezer is one of the more efficient of the practical freezer cycles, but the past mechanization of the Mechanical Freezer relied on two pistons operating with sine wave motion. An example of this is Ishiki et al (1987, U.S. Pat. No. 4,697,420). The cycle produced by this arrangement deviates from a true constant temperature compression. Another inventor has used a cam to move a secondary piston, but that was in an internal combustion engine C. H. Hutchinson (1922, U.S. Pat. No. 1,440,150).
The Mechanical Freezer cycle is composed of three processes. A constant temperature compression process, an expansion process, and a constant volume heating process (heat transfer from the load). The Mechanical Freezer of this invention closely approaches that ideal cycle by using power piston 106 and displacers 104 and 105. Power piston 106 is moved up and down by power input shaft 50. Displacers 104 and 105 are moved up and down by cam 108. When power piston 106 moving up and additional displacer 105 moving down come together, fluid is forced through additional heat sink 41 where it is cooled as it is compressed. When additional displacer 105 and primary displacer 104 come together, fluid is forced through primary heat sink 40 where it is cooled as it is compressed. After compression, the cooled fluid is expanded by power piston 106 along with displacers 104 and 105 moving down. When displacers 104 and 105 then move up, fluid is forced through load 30 and load 30 is cooled.
The advantage of the Mechanical Freezer is that it can cool the working fluid very efficiently because the cooled compression can approach constant temperature compression by using many additional compressors.
The preferred embodiment of the invention employs a two-stroke cycle divided into three processes. The first is the cooled compression process, the second is the expansion process, and the third is the heating process (cooling of the load). The heating process (cooling of the load) is heat addition at constant volume, and is the where the load gets cold.
The cooled compression process starts at about 15% of the travel up of power piston 106 and ends with power piston 106 at about top dead center. The expansion process starts with power piston 106 at about top dead center and ends at about 85% of the downward travel of power piston 106. The heat addition at constant volume process starts at about 85% of the downward travel of power piston 106 and ends at about 15% of the travel back up of power piston 106. The cooled compression process can be divided into many parts. FIGS. 1 to 4 show it divided into two parts the additional compression and the primary compression. The additional compression part starts at starts at about 15% of the travel up of power piston 106 and ends at about 50% of the travel up of power piston 106. The primary compression part starts at about 50% of the travel up of power piston 106 and ends with power piston 106 at about top dead center.
The above positions are all estimates and are given for descriptive purposes only. The actual position a process of the cycle may begin or end at may be different from those set out above. In addition, because primary displacer 104 does not operate sinusoidally, one process can be longer than another.
Cylinder 100 contains cylinder head 101, power piston 106, primary displacer 104, and additional displacer 105. Power piston 106 is driven with a sinusoidal motion through connecting rod 60 by power input shaft 50. Primary displacer 104 is driven through primary cam follower 110 by cam 108. Additional displacer 105 is driven through additional cam follower 111 by cam 108. The up and down motion of primary displacer 104 and additional displacer 105 is determined by the shape of the grooves in cam 108. Load 30 transfers cold out to a load not shown. Power input shaft 50 transfers work into the freezer from a power source not shown. Pressurizing valve 130 allows the complete engine to be pressurized.
Attached to cylinder 100 are three paths. The load path contains load isolation valve 114, load 30, heat exchanger low-pressure side 20, and fluid inlet port 120. The primary path contains primary inlet valve 118, primary heat sink 40, heat exchanger high-pressure side 90, and primary isolation valve 112. The additional path contains additional inlet valve 119, additional heat sink 41, and additional isolation valve 113.
Primary inlet valve 118 and primary isolation valve 112 isolate primary heat sink 40 from cylinder 100 during part of the cycle. Additional isolation valve 113 and additional inlet valve 119 isolate additional heat sink 41 from cylinder 100 during part of the cycle. Load isolation valve 114 and fluid inlet port 120 isolate load 30 from cylinder 100 during part of the cycle. Valve cam 70 and push rod 80 operate primary isolation valve 112, additional isolation valve 113, and load isolation valve 114 from power input shaft 50.
The primary displacer 104, along with primary cam follower 110, a groove in cam 108, primary heat sink 40, primary isolation valve 112, and primary inlet valve 118 make up the primary compressor. The additional displacer 105, along with additional cam follower 111, a groove in cam 108, additional heat sink 41, additional isolation valve 113, and additional inlet valve 119 make up an additional compressor. As many of these additional compressors as desired can be added to give intercooled compression approaching constant temperature compression.
The working fluid could be air or any gas or mixture of gases. The fluid in the system can be maintained at any pressure through pressurizing valve 130.
FIGS. 1 to 4 present the sequence of steps or processes occurring in the preferred embodiment of the freezer. The additional cooled compression process takes place between
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The first alternate embodiment of the freezer is the same as the preferred embodiment without heat exchanger low-pressure side 20 and heat exchanger high-pressure side 90.
The second alternate embodiment of the freezer is the same as the preferred embodiment without the additional compressor. The additional compressor contains additional displacer 105, along with additional cam follower 111, a groove in cam 108, additional heat sink 41, additional isolation valve 113, and additional inlet valve 119.
The third alternate embodiment of the freezer is the same as the preferred embodiment without heat exchanger low-pressure side 20, heat exchanger high-pressure side 90, and the additional compressor. The additional compressor contains additional displacer 105, along with additional cam follower 111, a groove in cam 108, additional heat sink 41, additional isolation valve 113, and additional inlet valve 119.
The fourth alternate embodiment of the freezer is the same as the preferred embodiment without the portion of the path connecting heat exchanger low-pressure side 20 to fluid inlet port 120 and pressurizing valve 130.
The advantage of the Mechanical Freezer is that it can cool the working fluid very efficiently.