for a typical slab coil design evaporator , the desired angle of the orifices of a distributor tube is selected based on testing of a vertical slab coil in which the refrigerant tubes are aligned in the direction of gravity with the inlet header lower than the outlet header . to accommodate the packaging constraints required for residential applications , a residential indoor evaporator may be constructed by using two slab coils in an a - frame design or a single slab coil bent into an arc design . shown in fig1 a - 1c are representations of an end view of an a - frame design or arc design residential indoor evaporator 10 having an inlet header 12 a , an outlet header 12 b spaced apart from the inlet header 12 a , and a plurality of refrigerant tubes 14 hydraulically connecting the headers 12 a , 12 b for refrigerant flow . an evaporator coil 16 , partially shown in fig2 and 3 , is defined by the plurality of refrigerant tubes 14 together with external fins 15 interconnecting the adjacent refrigerant tubes 14 . the evaporator 10 includes a distributor tube 20 in the inlet header 12 a , shown in fig2 - 7 , for improved refrigerant distribution . the above mentioned components of the evaporator 10 are typically constructed of a heat conductive material such as aluminum . each of the a - frame design and arc design provides an evaporator 10 having at least one apex 18 . the a - frame or arc design can be installed within a hvac plenum in various orientations with respect to the direction of gravity , in which the apex 18 may be up , down , horizontal , and any other orientation therebetween . with these varieties of possible orientations , the inlet header 12 a may be located above the outlet header 12 b , below the outlet header 12 b , or horizontal with the outlet header 12 b . the headers 12 a , 12 b are typically perpendicular to that of the direction of gravity , but the bottom header may be slightly angled toward the direction of gravity to facilitate condensate drainage . a standard angle designed for the orifices 22 of the distribution tube 20 relative to the refrigerant tube 14 may not necessarily work efficiently when used in all the various potential orientations of the evaporator 10 . it was found that only certain range of angles of the orifices 22 of the distribution tube 20 relative to the refrigerant tube 14 are acceptable for each of the various evaporator coil 16 orientations . in other words , orifice angles are application specific ; therefore , the desired orifice range of angles has to be calculated for each specific orientation of the evaporator 10 . with reference to fig2 - 4 , it is believed that the liquid phase 24 of a two - phase refrigerant flowing through the distributor tube 20 tends to migrate to the bottom of the interior surface 28 of the distributor tube 20 due to gravity . it is suspected that the liquid phase 24 does not necessary puddle on the bottom or low spot of the distribution tube 20 , but instead it is pressed against and rides up a portion of the interior surface 28 of the distributor tube 20 by the flow of refrigerant through the distributor tube 20 , thereby forming a liquid refrigerant cross - sectional profile 30 much like a crescent moon with its apex on the bottom . the limit would be annular flow where the liquid distributes around the entire peripheral internal surface 28 of the distribution tube 20 , but more typically a thicker layer would exist on the bottom . it was found that if the orifices 22 were facing in a direction other than between 45 to 315 degrees with respect to the opposite direction of gravity being 0 degree , mostly vapor phase refrigerant tend to exits the orifices 22 migrating toward the refrigerant tubes 14 . this is undesirable because optimal heat transfer efficiency is obtained when the refrigerant entering the refrigerant tubes is in a substantially liquid phase . with reference to fig3 , it was surprisingly found that when the orifices 22 are oriented substantially in the direction of gravity , the pressure and momentum of the refrigerant flowing through the distributor tube 20 pushes the liquid phase refrigerant out of the distributor tube 20 through the orifices 22 toward the refrigerant tubes . the refrigerant remains substantially in liquid phase until it reaches the refrigerant tubes 14 , at which point the liquid phase refrigerant starts to absorb heat and vaporizes , thereby providing optimum heat transfer and even temperature distribution across the evaporator coil 16 . with reference to fig4 , during periods of high refrigerant flow , the liquid refrigerant cross - sectional profile 30 occupies the interior surface 28 of the distributor tube 20 from 45 to 315 degrees with respect to the opposite direction of gravity being 0 degree . during normal operating conditions , the liquid refrigerant cross - sectional profile 30 occupies the interior surface 28 of the distributor tube 20 from 90 to 270 degrees . an aspect of the invention provides a means to transport the liquid phase refrigerant from the distributor tube 20 to the refrigerant tubes 14 for efficient boiling and thus improved heat transfer performance regardless of the orientation of the a - frame or arc evaporator coil evaporator . this can be achieved by having orifices 22 at angles from 45 to 315 degrees , preferably between 90 to 270 degrees , with respect to the opposite direction of gravity being 0 degree , along the distributor tube 20 to ensure that at least one , but preferably a group , of orifices 22 is substantially oriented within the liquid refrigerant cross - sectional profile 30 . by having one or more orifices within the liquid profile 30 , the refrigerant flowing through the distributor tube 20 will push the liquid phase refrigerant through the orifices 22 and toward the refrigerant tubes . fig5 shows a cylindrical refrigerant distributor tube 20 extending along a substantially central axis ( a - axis ). pairs of orifices 22 are substantially uniformly spaced along the length of the distributor tube 20 , in which each pair of orifices 22 is located about its respective point on the a - axis . within each pair of orifices 22 , one of the orifices 22 may be oriented 90 to 180 degrees apart from the other with respect to the pair &# 39 ; s respective point on the a - axis . furthermore , each pair of orifices 22 may be rotated 90 to 180 degrees from the adjacent pair of orifices 22 . fig6 shows a cylindrical refrigerant distributor tube 20 extending along the a - axis . groups of four ( 4 ) orifices 22 are substantially uniformly spaced along the length of the distributor tube 20 , in which each group of orifices 22 is located about its respective point on the a - axis . within each group of four ( 4 ) orifices 22 , each of the orifices 22 may be oriented 90 degrees apart from the adjacent orifice 22 with respect to the group &# 39 ; s respective point on the a - axis . furthermore , each group of ( 4 ) orifices 22 may be rotated 45 degrees from the adjacent group of ( 4 ) orifices 22 . fig7 shows a cylindrical refrigerant distributor tube 20 having a plurality of orifices 22 spiraled along the tube . with respect to an end view of the a - axis , each succeeding orifice 22 may be offset 45 to 180 degrees from the preceding orifice 22 . with the above configurations of orifices 22 on the distributor tube 20 or any configuration that provides at least one orifice 22 in the desired direction regardless of the orientation of the evaporator 10 would improve the distribution of refrigerant though the refrigerant tubes 14 . therefore , if the evaporator coil 16 is positioned in any one of the various possible orientations , at least one of the orifices 22 would be located within the liquid refrigerant cross - sectional profile 30 . while this invention has been described in terms of the preferred embodiments thereof , it is not intended to be so limited , but rather only to the extent set forth in the claims that follow .