Abstract:
Methods and systems for cooling gas chromatography ovens that comprise a housing having a fluid entry and a sleeve positioned within the housing to provide a fluid gap between the inner surface of the housing and the outer surface of the sleeve, where the sleeve is coupled to the fluid entry, and where a cooling fluid from the fluid entry traverses the inner layer of the sleeve and thereafter the outer layer of the sleeve via the fluid gap. In one embodiment, the housing includes at least one adjustable fluid exit, and the fluid gap is in fluid communications with the fluid exit(s). The fluid entry and the sleeve can be concentric, and the sleeve can include a heating element. A fan can be positioned to drive the cooling fluid from the fluid entry.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of U.S. patent application Ser. No. 11/122,148 filed May 4, 2005, which claims the benefit under 35 U.S.C. §119(e) of the U.S. Provisional Patent Application Ser. No. 60/521,479 filed May 4, 2004, all of which are herein incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to gas chromatography, and more specifically to an improvement in a gas chromatography oven to achieve improved heat exchange.  
       BACKGROUND OF THE INVENTION  
       [0003]     Gas chromatography is performed in a special instrument where a small amount of liquid mixture is injected into an apparatus where it is volatized in a heated chamber. The volatized mixture is swept through a column in a stream of gas, such as helium or neon under conditions where its components separate into pure compounds. The column is located in a heated oven in order to facilitate the separation. Just before each compound exits the instrument, it passes through a detector, which sends an electronic message to the recorder, which responds by printing a peak on a piece of paper identifying the compound.  
         [0004]     Typically the column is heated by placing the column in an oven. The heat facilitates compound separation by raising the column temperature and speeding up the compounds in the mixture. For precise work, column temperature may be controlled to within tenths of a degree. The optimum column temperature is dependant upon the boiling point of the sample. Generally, a temperature slightly above the average boiling point of the sample results in an elution time of 2-30 minutes. If a sample has a wide boiling range, then temperature programming can be useful. The column temperature is increased (either continuously or in steps) as separation proceeds.  
         [0005]     Accordingly, analytes of interest are assayed at different temperatures, including high temperatures such as 500° C., and it is necessary to cool the oven and the column prior to testing additional samples. Long cooldown periods are problematic because they lengthen the sample cycle time reducing instrument productivity. Delay is compounded in high throughput analysis where a gas chromatograph is needed to analyze a large number of samples containing the same or different analytes of interest. Users waste time waiting for the column and oven to cool prior to running additional samples.  
         [0006]     Ventilation systems including fans have been added to the gas chromatograph to blow air into the oven and onto the column between runs. However, conventional designs are slow to cool for there are considerable flow restrictions which impede the air flow throughout the oven. Furthermore, certain designs allow the cooling inlet air to mix with exhausting air resulting in a slower, less efficient cool down of the oven. Moreover, temperature gradients may form in the oven reducing the consistency or uniformity of the cooling down components.  
         [0007]     Prior art of interest includes one system which relates to a chromatography oven which includes a fan within a housing adjacent to rear walls, an ambient air intake vent in the rear wall, and an exhaust vent within a rear corner of one of the side walls adjacent to the rear wall for exhausting the tangential flow of air created by the rotating fan. However, this design has considerable flow restrictions which impede the air flow throughout the oven resulting in a less efficient cool down.  
         [0008]     Of further interest is another prior art system which relates to an apparatus having a first compartment including a chromatography oven with fan for circulating heated air over the columns while the oven is closed and for drawing in ambient temperature cooling air in the first compartment into the oven while the oven is open. Ambient air is drawn into a tortuous path in the first compartment. Cooling air from the second compartment flows into the first compartment via openings in the baffle. The cooling air flows over the oven exterior and is at least partially drawn into the oven by an oven fan while the oven is open. The oven heater, coaxial with the blades, is located between an oven wall and blades. A ring baffle, having approximately the same diameter as and coaxial with the blades, is located between the wall and the blades. A fan outside of the oven draws air from the oven through an outlet while the oven is open. The second fan is separated from an inlet for the oven by a baffle having an opening through which air is drawn by the second fan while the oven is closed. The second compartment includes a casing for fluid flow controllers for the columns, which casing is maintained at constant temperature by ambient air drawn around the second compartment. However this design impedes air flow because the air entering the oven counters air flow leaving the oven reducing the efficiency of the cooling. Furthermore, the baffle impedes airflow and produces a temperature gradient in the oven which results in a less efficient cool down. Moreover, this device requires two fans to circulate airflow which takes up additional energy and is noisy.  
         [0009]     Of further interest is another prior art system relating to gas chromatography (GC) system employing a low-thermal-mass oven in which intake and exhaust vent apertures are aligned with respect to the rotational axis of the stirring fan. The poppets of the vent dynamically vent to ambient the air-flow generated by the stirring fan. The geometry of the vents cooperates with the axial and radial components of the stirring fan to promote conical vortex air flow, to facilitate mass-flow interchange with ambient air. However, the ventilation system includes a bulky vent servo in order to drive a carriage assembly which opens a front exhaust poppet. Exhaust leaves the front of the oven never circulating back over the oven skin resulting in reduced efficiency.  
       SUMMARY OF THE INVENTION  
       [0010]     It is an object of the present invention to provide an oven that reduces or eliminates air flow restrictions which impede air flow within a gas chromatography oven.  
         [0011]     Another object of the present invention is to provide a gas chromatography oven that reduces mixing of inlet air and exhausting air.  
         [0012]     Another object of the present invention is to provide a gas chromatography system which is highly efficient.  
         [0013]     Another object of the present invention is to provide a gas chromatography oven that controls heat exchange between the airflow and the gas chromatography oven components.  
         [0014]     The present teachings include gas chromatography ovens that comprise a housing having a fluid entry and a sleeve positioned within the housing to provide a fluid gap between the inner surface of the housing and the outer surface of the sleeve, where the sleeve is coupled to the fluid entry, and where fluid from the fluid entry traverses the inner layer of the sleeve and thereafter the outer layer of the sleeve via the fluid gap. In one embodiment, the housing includes at least one fluid exit, and the fluid gap is in fluid communications with the fluid exit(s). The fluid entry and the sleeve can be concentric, and the sleeve can include a heating element. In an embodiment, also included is a fan positioned to drive at least one fluid from the fluid entry into the sleeve.  
         [0015]     The gas chromatography oven housing can include a wall, at least a portion of which is adjustable to prevent fluid from entering the fluid entry. Further, the oven housing can include at least one fluid exit, and, a wall at least a portion of which is adjustable to prevent fluid from exiting the fluid exit(s).  
         [0016]     The present teaching also include methods of cooling a gas chromatography oven, where the method comprises providing a housing having a fluid entry, positioning a sleeve within the housing to provide a fluid gap between the inner surface of the housing and the outer surface of the sleeve, where the sleeve is coupled to the fluid entry, and where fluid from the fluid entry traverses the inner layer of the sleeve and thereafter the outer layer of the sleeve via the fluid gap, and, providing a cooling fluid to the fluid entry. Positioning can include concentrically positioning the sleeve and the fluid entry. The methods can also include controlling a fan positioned at the fluid entry to drive the cooling fluid from the fluid entry. In some embodiments, the methods include adjusting at least a portion of at least one wall of the housing to facilitate entry of the cooling fluid to the fluid entry, and/or adjusting at least a portion of at least one wall of the housing to facilitate exit of the cooling fluid from at least one fluid exit, where the at least one fluid exit is in fluid communications with the fluid gap.  
         [0017]     The objectives of the present invention are met by providing a gas chromatography oven comprising: a housing having two end walls and a peripheral wall, a sleeve disposed within the housing, the sleeve having a peripheral wall spaced apart from the peripheral wall of the housing; and a fluid path defined by an interior of said sleeve, a first gap between at least one end wall and the sleeve, and a second gap between the peripheral wall of the sleeve and the peripheral wall of the housing, wherein air is forced through the sleeve, through the first gap between at least one end wall and the sleeve, and through the second gap between the peripheral wall of the sleeve and the peripheral wall of the housing. The peripheral wall of the housing may further comprise four side walls having a first length and the sleeve has a second length, wherein the first length is longer than the second length. The peripheral wall of the housing may further comprise a front wall and a rear wall having a first height, and the sleeve has a second height, wherein the first height is longer than the second height. The peripheral wall of the housing further comprises a front wall and rear wall having a first width and the sleeve has a second width, wherein the first width is longer than the second width. The peripheral wall of the housing may further comprise at least three side walls and the sleeve is mounted in the housing to form at least three gaps between the sleeve and at least three side walls. The oven may further comprise a sleeve mounted in the housing to form a rear gap between the sleeve and a rear wall. The sleeve may further comprise a top surface, a bottom surface, and two side surfaces. The sleeve may be in the shape of a tube, such as a rectangular tube. The sleeve may comprise a first end positioned adjacent to a first end wall and a second end positioned adjacent to a second end wall. The sleeve may have a first opening adjacent to one end wall and a second opening adjacent to the other end wall. The oven may further comprise a heating element positioned adjacent an end wall and adjacent to the sleeve. The sleeve may surround the heating element. The housing may further comprise at least three side walls, wherein at least three gaps are positioned between the sleeve and the at least three side walls. The oven may further comprise a fan positioned adjacent to one end wall, wherein the sleeve is in coaxial alignment with the fan. One end wall may further comprise a central door. The oven may further comprise a fan having a blade and a central axis perpendicular to the blade, the blade having a first length equal to the radius of the fan. Optionally, the sleeve is in the shape of a tube having a radius which is longer than the radius of the fan. The oven may comprise at least one gap which traverses the apparatus from end wall to end wall. The first and second gaps may have a width of between about 0.5 cm to 20 cm, preferably about 2 cm. The second gap may have a width of between about 0.5 cm and about 20 cm and traverses the apparatus from end wall to end wall, preferably about 2 cm. The oven may further comprise a fan that has an adjustable rate of rotation. The oven may be disposed within a gas chromatography system comprising a carrier gas delivery device; an injector system; and a detector system.  
         [0018]     The objectives of the present invention are met by providing a gas chromatography oven comprising: a housing having a front wall, a rear wall, and four side walls; and a sleeve comprising a top surface, a bottom surface and two side surfaces mounted within the housing, wherein the four side walls have a first length longer than the length of the top surface, bottom surface and two side surfaces such that at least three gaps are formed between the sleeve and the housing. The four side walls may have a first width longer than the width of the top surface, bottom surface and two side surfaces such that at least three gaps are formed between the sleeve and the housing. The at least three gaps are located between the sleeve and the side walls. At least one gap is located between the sleeve and the front wall. Optionally, at least one gap is located between the sleeve and the rear wall. Optionally the oven comprises four gaps located between the sleeve and the four side walls. The oven further comprises a housing having a longitudinal axis between the four side walls, and the sleeve has a longitudinal axis between the top surface, bottom surface and two side surfaces, wherein the longitudinal axis of the housing is in coaxial alignment with the longitudinal axis of the sleeve. The rear wall is separable from the housing. Optionally, the rear wall further comprises a door. A fan may be disposed inside the housing adjacent to the rear wall. Optionally, the fan is connected to a variable speed motor. Furthermore, the oven may further comprise a heating element adjacent to the fan. The oven may further comprise a baffle adjacent to the heating element. The oven may further comprise gaps connected to a plenum positioned adjacent to the rear wall. The oven may be further disposed within an external housing, wherein the external housing connects at least one carrier gas supply; at least one sample injection system; and at least one detector system. The external housing may further comprise a raised bottom surface and an exhaust chute adjacent to the bottom surface.  
         [0019]     The objectives of the present invention are further met by providing a gas chromatography system comprising a gas chromatography oven having a housing having two end walls and a peripheral wall, a sleeve disposed within the housing, the sleeve having a peripheral wall spaced apart from the peripheral wall of the housing; and a fluid path defined by an interior of the sleeve, a first gap between at least one end wall and the sleeve, and a second gap between the sleeve and the peripheral wall of the housing, wherein air is forced through the sleeve, through the first gap between at least one end wall and the sleeve, and through the second gap between the sleeve and the peripheral wall of the housing; and at least one additional component selected from the group consisting of carrier gas supply, pressure regulator, flow controller, rotometer, gas flow line, injector system, autosampler, injector, column, detector, soap-bubble meter, electrometer, ADC, data system and combinations thereof. The system may further comprise a detector selected from the group consisting of flame ionization detector, thermal conductivity detector, electron capture detector, environmental specific detector, photoionization detector, nitrogen phosphorous detector, and combinations thereof. The system may further comprise a raised external housing comprising an exhaust chute adjacent to the bottom of the external housing. The system may further comprise an oven comprising a fan, a baffle, and a heater in coaxial alignment with the sleeve.  
         [0020]     The objectives of the present invention are further met by providing a method of cooling a gas chromatography oven comprising: blowing air through a fluid path defined by an interior of a sleeve, a first gap between at least one end wall and the sleeve, and a second gap between the sleeve and a peripheral wall of a housing, wherein air is forced through the sleeve, through the first gap between at least one end wall and the sleeve, and through the second gap between the sleeve and the peripheral wall of the housing. The method may further include: directing the air towards a second gap. The step of blowing air may further comprise the step of changing air speed by adjusting a motor. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a schematic view of a gas chromatography system of the present invention.  
         [0022]      FIG. 2  is a schematic top view of a gas chromatography oven of the present invention.  
         [0023]      FIG. 3  is a front plan view of the gas chromatography oven of  FIG. 2 .  
         [0024]      FIG. 4  is an isometric view of the gas chromatography oven of  FIG. 2  with the sleeve shown partially in phantom.  
         [0025]      FIG. 5  is a front view of a gas chromatography oven of  FIG. 2  with components in coaxial alignment.  
         [0026]      FIG. 6  is a front view of a gas chromatography oven of  FIG. 2  with components in coaxial alignment.  
         [0027]      FIG. 7  is a front view of a gas chromatography oven of  FIG. 2  with components in coaxial alignment.  
         [0028]      FIG. 8  is a partial cross-sectional side view taken along line A-A′ of  FIG. 7  with plenum.  
         [0029]      FIG. 9  is a schematic view of gas chromatography system with oven of  FIG. 2 .  
         [0030]      FIG. 10  is a cooling profile graph of oven temperature over time using system of  FIG. 9 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]     Referring now to  FIG. 1 , a schematic view of a gas chromatography system  10  of the present invention is shown. Carrier gas supply  12  is shown connected to oven  100 . Carrier gases typically include noble gases such as helium, neon, or argon, however any suitable gas may be used. Various control devices such as pressure regulator  14 , flow controller  16 , and rotometer  18  regulate and measure the rate of fluid flow between supply  12  and oven  100 . Gas flow line  20  enters the oven and is connected to injector system  24 . Injector system  24  is provided to load a sample with analyte(s) of interest into oven  100 , which may include an autosampler. Gas from first gas flow line  20  and sample with analyte of interest combine in injector  23  and pass into column  32  located in oven  100  and connected to detector  28 . A wide range of suitable detectors  28  for sensitivity and selectivity may be used with the present invention, including but not limited to a flame ionization detector, thermal conductivity detector, electron capture detector, environmental specific detector, photoionization detector, nitrogen phosphorous detector, and combinations thereof. Gas chromatography system  10  may further include soap-bubble meter  34  for measuring the flow of gas at ambient temperature and pressure over a wide range of flow rates. Recorder  36  is shown connected to electrometer or bridge  38 , which is connected to ADC  40  and data system  42 , all for converting a signal into qualitative information about an analyte of interest. Sleeve  60  is added to improve heat exchange during the cooling cycle.  
         [0032]     Referring now to  FIG. 2 , a schematic top view of gas chromatography (GC) oven  100  is shown comprising a housing  101  having two end walls  1  &amp;  2  and peripheral wall  3 . Sleeve  60  is disposed within housing  101 , sleeve  60  having a peripheral wall  4  spaced apart from the peripheral wall  3  of housing  101 . As used herein the term sleeve means a passageway that allows air to pass through, no particular shape or size is necessary. A fluid path defined by an interior of the sleeve  111 , a first gap  5  between at least one end wall  2  and sleeve  60 , and a second gap  6  between sleeve  60  and the peripheral wall  3  of housing  101  is shown. In the illustrated embodiments, air is moved in the direction of arrows  126  through sleeve  60 , through the first gap  5  between at least one end wall  2  and sleeve  60 , and into the second gap  6  between sleeve  60  and peripheral wall  3  of housing  101 .  
         [0033]     With reference to  FIG. 2  and  FIG. 3 , housing  101  is shown having a front wall  102 , a rear wall  104 , and two side walls  106 ,  108 . Housing  101  comprises two additional walls  110  and  112  (not shown in  FIG. 2 ). Sleeve  60  has a top surface  114  (not shown in  FIG. 2 ), a bottom surface  116  (not shown in  FIG. 2 ) and two side surfaces  118  and  120  mounted within housing  100 . The four side walls  106 ,  108 ,  110 , and  112  have a first length  120  longer than the length of the top surface  114  (not shown in  FIG. 2 ), bottom surface  110  (not shown in  FIG. 2 ) and two side surfaces  118  and  120  such that at least three gaps  122  are formed between sleeve  60  and housing  101 .  
         [0034]     With continued reference to  FIGS. 2 and 3 , gaps  122  may be positioned above, below, in front of, behind, and along the sides of sleeve  60  between housing  101 . Sleeve  60  is mounted within housing  101  by ways in which one of ordinary skill in the art would mount a sleeve, including soldering and bolting techniques. The four side walls of housing  101  have a first width  124  longer than the width of the top surface, bottom surface and two side surfaces of sleeve  60  such that at least three gaps  122  are formed between sleeve  60  and housing  101 . Three or more gaps  122  may be located between sleeve  60  and side walls  106 ,  108 ,  110 ,  112 . At least one gap  122  may also be located between sleeve  60  and front wall  102 . At least one gap  122  may also be located between sleeve  60  and the rear wall  104 . Moreover, oven  100  may be configured to have four gaps  122  located between sleeve  60  and the four side walls  102 ,  104 ,  106 ,  108 .  
         [0035]     Still referring to  FIG. 2 , gap  122  is shown between sleeve  60  and housing  101 . Gap  122  is of predetermined shape and size. Here, gap  122  is shown traversing the interior length, width, and height of housing  101 . The width between housing  101  and sleeve  60  can be between about 0.5 cm to 30 cm, but in some embodiments may be about 2 cm and 10 cm, and in further embodiments about 4 cm. During ventilation, ambient air enters through a sliding door (not shown in  FIG. 2 ) built into wall  104 , then travels through the interior portion  111  of sleeve  60  in the direction of arrow  126 . Upon collision with front wall  102 , the cooling air moves up, down, and laterally into gaps  122  between housing  101  and sleeve  60 . The cooling air then travels back through oven  100  over oven skin  103  into a plenum (not shown in  FIG. 2 ) resulting in a thermal cool down.  
         [0036]     Referring now to  FIG. 3 , a front plan view of the gas chromatography oven of  FIG. 2  is shown. Housing  101 , made to predetermined dimensions, is shown having at least four side walls  106 ,  108 ,  110 , and  112 . Sleeve, also of predetermined dimensions, has a top surface  114 , a bottom surface  116  and two side surfaces  118  and  120  mounted within housing  101 . The four side walls  106 ,  108 ,  110 , and  112  have longer and wider dimensions than the length of the top surface  114 , bottom surface  116 , and two side surfaces  118  and  120  such that at least three gaps  122  are formed between sleeve  60  and housing  101 .  
         [0037]     Referring now to  FIG. 4  there is shown an isometric view of the gas chromatography oven of  FIG. 2  with the sleeve  60  shown partially in phantom. Housing  101 , made to predetermined dimensions, is shown having at least four side walls  106 ,  108 ,  110 , and  112 . Sleeve  60 , also of predetermined dimensions, has a top surface  114 , a bottom surface  116  and two side surfaces  118  and  120  mounted within housing  101 . The four side walls  106 ,  108 ,  110 , and  112  have longer, wider and higher dimensions than the length of the top surface  114 , bottom surface  116 , and two side surfaces  118  and  120  such that at least three gaps  122  are formed between sleeve  60  and housing  101 . Oven  100  is shown having a first opening  130 . Front wall  102  of housing  101  acts as an access door to oven  100  opening and closing first opening  130 , and may be attached to housing  101  by one or more hinges. Sleeve  60  is also shown having a front or first opening  132  adjacent to the first opening  130 . Also sleeve  60  comprises a second opening  134  adjacent to rear wall  104 . Fluid entry or door  444  is shown in rear wall  104  which is opened during the ventilation process to provide cooling air to oven  100 . Optionally fluid entry  444  may be in coaxial alignment with fan shaft (not shown in  FIG. 4 ).  
         [0038]     With continued reference to  FIG. 4  at least one fluid exit  446  is shown in housing  101 . Fluid exit  446  is of predetermined shape and size and positioned in fluid communication with gap  122 . Fluid exit  446  can be positioned within at least a portion of at least one wall of housing  101  to facilitate exit of the cooling fluid from at least one fluid gap  122 , where the at least one fluid exit  446  is in fluid communications with the fluid gap  122 . Optionally, second, third and fourth fluid exits  446  may be positioned in housing  101 . Fluid exit  446  may comprise a door  447  capable of adjusting fluid flow passing through the fluid exit. Door  447  may be configured as a controllable sliding door suitable for opening and closing fluid exit  446 .  
         [0039]     Referring now to  FIG. 5 a  front view of a gas chromatography oven of  FIG. 2  with components in coaxial alignment along axis A-A′ is shown. Sleeve  60  is disposed within oven  100 . Fan  180  is shown located within oven cavity  182  between rear wall  104  and second opening  134  of sleeve  60 . Fan  180  may be a conventional fan used in gas chromatography ovens and have one or more fan blades  181  for directed air through oven  100  and sleeve  60 . Fan  180  rotates about a fan axis (not shown in  FIG. 5 ). When the ventilation system is open, fan  180  directs ambient air into inner portion  111  of sleeve  60 . The predominant flow directs air towards front wall  102  which, when closed, redirects the air as described herein. In some embodiments, the fan axis extends through intake and exhaust apertures (not shown in  FIG. 5 ) in coaxial alignment with the aperture centers. In alternative embodiments, the fan axis extends through intake and exhaust apertures without being aligned with the aperture centers.  
         [0040]     Referring now to  FIG. 6 a  front view of a gas chromatography oven of  FIG. 2  with components in coaxial alignment along axis A-A′ is shown. Sleeve  60  is disposed within oven  100 . Fan  180  is shown located within oven cavity  182  between rear wall  104  and second opening  134  of sleeve  60 . Heating element  158  is mounted inside oven  100  in close proximity to rear wall  104  and fan  180 . Heater  158  may be any heater suitable for use in a gas chromatography oven, such as an electric coil heater. Heater  158  is supplied with sufficient current to enable the temperature of the air in oven  100  to heat up to about 500° C. In some embodiments, heater  158  includes a resistive heater and an amplifier. To either end of heater  158  shields may be added to protect column (not shown in  FIG. 6 ) from direct radiant heat. Baffle  190  is also shown, which may include an integral protective screen in the center portion. Baffle  190  may be made of stainless steel and attached to housing  101  between top side wall  112  and bottom side wall  110  by fasteners known in the art. Heater  158  is positioned between fan  180  and baffle  190 . Baffle  190  is used to constrain the flow from the fan and enhance the pressure gradient across oven  100 . In embodiments, the internal elements, including sleeve  60 , fan  180 , heater  158 , and baffle  190  are in coaxial alignment within housing  101  along axis A-A′.  
         [0041]     Referring now to  FIG. 7 , a front view of a gas chromatography oven of  FIG. 6  with components in alignment is shown. The internal elements common to each of the embodiments of gas chromatography oven are shown including sleeve  60 , fan  180 , heater  158 , and baffle  190  substantially aligned within housing  101  along axis A-A′. Column  232  is positioned in the interior of oven  100  adjacent to baffle  190 . Column  232  may be held in place by brackets (not shown in  FIG. 7 ) or other means known in the art.  
         [0042]      FIG. 8  is a partial cross-sectional view taken along line A-A′ of  FIG. 7 . The only basic difference between the embodiment shown in  FIGS. 6 &amp; 7  is the use of plenum chamber  160  to vent air through the back portion and bottom of housing  101 . Plenum chamber  160  as shown in  FIG. 8  has a depth from plenum wall  166  to rear wall  104 . During ventilation, air travels in the direction of arrow  126 . Ambient air passes through sleeve  60 , then passes over oven skin  103  of oven  100  while returning to plenum chamber  160  prior to exiting the apparatus. Fan motor  400  may be a brush motor or a brushless motor, and in embodiments, a variable speed brushless motor capable of spinning fan  180  between about 1000 RPM to about 4500 RPM and above. Shown below in  FIG. 9  is a more preferred embodiment where plenum chamber  160  is configured adjacent to fan  180  within housing  101 .  
         [0043]      FIG. 9  is a schematic view of gas chromatography system with oven of  FIG. 2 . Gas chromatography oven  100  is shown positioned within gas chromatography exterior housing unit  300 . Exterior housing  300  may be configured to accommodate some or all of the various components shown in  FIG. 1  above. Oven  100  can be made of materials which enhance dynamic performance. Oven walls have a thickness ranging from about 1 cm to about 8 cm, and in some embodiments, about 2 cm to about 2.5 cm between the inner edge  701  of insulator  305  and outer face  702 . The outer face  702  or skin consists of a metal, e.g. aluminum or steel, or a high temperature plastic, typically having a thickness of about 2 mm. Positioned adjacent to outer face  702  is insulator  305  made of thermal ceramic material such as microporous insulation designed for use in high temperature applications. Insulator  305  is between about 0.5 cm to about 20 cm thick, and in some embodiments, about 3.5 cm. In some embodiments insulator  305  is made of BTU-Block Board 1807/18 ceramic material having a relatively low thermal conductivity and heat loss. It has been found that this brand of thermal ceramic material promotes a highly efficient cool down due to its relatively low thermal mass and heat storage capacity. Although other thermal ceramic products are suitable for use in the present invention, such as a ceramic fiber known as Kaowool blanket, other ceramic fibers may be less preferred. In some embodiments, insulator  305  is disposed throughout housing  101  inside front wall  102 , rear wall  104 , side walls  106 ,  108 ,  110  and  112 . Interior edge  701  of insulator  305  can make up the interior edge of front wall  102 , rear wall  104 , side walls  106 ,  108 ,  110  and  112 .  
         [0044]     Still referring to  FIG. 9 , rear wall  104  is a sliding member capable of sliding away from the remaining portions of oven  100 . During ventilation, rear wall  104  is extended away from oven  100  and its components. The extended position allows air to travel through external housing  300  into oven  100  and sleeve  60 . Optionally, one or more doors may be positioned in rear wall  104  for ventilation.  
         [0045]     After a run, a cooling cycle occurs where heating element  158  is turned off and rear wall  104  is opened. Ambient air is pulled by fan  180  from outside oven  100  through exterior housing unit  300  in the direction of arrows  126 . Air circulates past open rear wall  104 , through the apparatus and into sleeve  60 . The airflow is extremely direct and not hindered by counter airflow. The heat transfer is compounded by the dual action of cooler air contacting the outside of sleeve  60 , as well as insulator  305 . In some embodiments, the airflow is directed out the back of the oven into a plenum portion  160  configured adjacent to fan  180 . In some embodiments, trap door  650  is open during the cool down cycle such that cooling air is capable of venting through exhaust shoot  655  located in the lowest portion of exterior housing unit  300 . Accordingly, in comparison to conventional units, exterior housing unit  300  is raised to accommodate exhaust shoot  655 .  
         [0046]      FIG. 10  is a graph of an oven cooling profile using an embodiment of the present invention. Four cool down profiles are shown for four different fan rates including 3915 RPM, 698 RPM, 2813 RPM, and 1401 RPM. Rapid heat exchange between the oven and surrounding environment using different fan speeds was observed.  
         [0047]     Without departing from the spirit and scope of this invention, one of ordinary skill in the art can make various changes and modifications to the invention to adapt it to various usages and conditions. As such, these changes and modifications are properly, equitably, and intended to be, within the full range of equivalents of the following claims.