【正文】 d along the right edge. The air inside the condenser section is almost 18176。Vertical Orientation. The next series of infrared images, Figures 13,14,15,16,17,18, show the operation of the air infiltrated flat heat pipe in a vertical orientation. For this orientation, the evaporator section was located below the condenser section. The heat input range was again 200–800 W. Figure 13 depicts the large gas loaded case at a heat input of 200 W. As can be seen, the only active portion of the condenser region is in the lower left corner adjacent to the evaporator section (not seen because it was covered with thermal insulation hence the evaporator appears cooler than the condenser on the IR videotape). The heat pipe condenser was operating asymmetrically and the air appears to cover most of the condenser heat transfer area. Figure 14 shows the condenser surface to be more active at 200 W for the small gas loading case. In fact, two thirds of the condenser surface is believed to be actively condensing as indicated by the fairly uniform surface temperature on the order of 33176。C. In Fig. 11, the active condenser surface temperature is in the 100–105176。C. This emissivity was . The IR camera system was now calibrated. Periodically, the emissivity would be checked by paring thermocouple data to IR data. There was a fluctuation in surface emissivity between and . Care was taken so as not to operate the flat heat pipe above 101 kPa internal conditions in order to prevent any puffing out along the heat pipe flat surfaces which might result in an emissivity calibration error, ., partial hemispherical surfaces. It was decided to only report the temperatures in this particular study using the IR camera since the IR camera data was within +/–1176。C. Two layers of Monel screens were used, 40 mesh and 120 mesh. The purpose of the two different screen sizes was to design a wick of varying permeability. Long copper bars with fine radius edges were utilized to facilitate bending the heat pipe to the required dimensions. The two layers of screen were then placed on top of the vessel. The 120 mesh screen was then placed on the top of the 40 mesh screen to aid in the development of the capillary pumping head of this screen wick. The screen was then tackwelded to the vessel wall in regular intervals between the pin spacer locations. The Monel sheets and screens were then punched, making holes in the locations where the support pins were to be TIG welded. The mm diameter pins were then cut to the proper length, milled, and deburred to fit into the necessary space. Figure 3 depicts a section of the Monel sheets, screens and pins (Boughey, 1999). The gap size between the Monel sheets was approximately of mm. There were 15 rows, three pins per row of Monel pins, TIG welded to the face sheets. Figure 3. The sides of the two separate halves were welded together, carefully sequencing the welds and using a heat trap to minimize deformation. After this, the ends were welded on and the fill fitting was welded snug to the end. The pins were then placed in their proper spots and TIG welded on both sides of the heat pipe. Leaktesting and charging consisted in the fabrication of a charging apparatus. A mm nipple was fitted to the fill end of the heat pipe (condenser) and mated to an air pressor. The heat pipe was then pressurized for leak testing. To leak test, soapy water was applied to the pressurized heat pipe in order to detect the leaks. Leaks would form bubbles in the soapy water. The heat pipe was allowed to sit pressurized over night and it was discovered that some very small leaks did exist. These were found by injecting a small amount of R134a into the heat pipe and sniffing it with a Yokogawa refrigerant leak detector. The leaks were then fixed. A bourdon tube pressure gage was mounted on the fill neck. Charging the heat pipe with working fluid was performed fairly simply. First, the heat pipe and charging assembly were mated to an oil diffusion vacuum pump and evacuated. In the fluid charging column was placed the correct amount of water to charge the heat pipe. These amounts were measured and marked, taking into account the volume that would occupy the fittings as well as the heat pipe. Once evacuation was plete, the valve attached to the vacuum pump and the valve attached to the heat pipe were closed and the vacuum pump was shut off. The valve attached to the fluid column was then opened, and the vacuum inside the fittings drew the water in to fully fill the pipe volume between the fittings. The heat pipe valve was then opened slightly to bleed in the necessary charge (as marked on the column). All valves were then closed and the charging apparatus removed. The heat pipe was charged to 125 percent of the porous volume that the screen wick contained. Thirtyeight (38), 20 AWG type K thermocouples were mounted on the heat pipe as shown in Fig. 4. The thermocouples were soldered in place. The entire heat pipe was then painted flat black using Krylon paint. The emissivity of the black surface was measured as at 25176。 revised: May 13, 2002In the satellite or energy conversion industries flat heat pipes may be utilized to transfer heat to the thermal sink. In this investigation, a large flat heat pipe, m m m, fabricated from 50 mil Monel 400 metal sheets and Monel 400 screens was videographed at horizontal and vertical orientations with an infrared video camera. The heat pipe evaporator section consisted of a m m area (one heated side only) while the side opposite the heated section was insulated. The remaining area of the heat pipe served as the condenser. In the horizontal orientation the heated section was on the bottom. In the vertical orientation the evaporator was aligned below the condenser. The sequence of photographs depicts heat inputs ranging from 200 W to 800 W, and the effect of air infiltration on heat pipe operation for both orientations. For the horizontal orientation, the air is seen to rece