The effects of entrapped air on the heating rate, lethality and cold spot in bricks packaged in retort pouches were determined using silicone rubber bricks (10 x 14.5 x 2cm), with 5 thermocouples positioned from the geometric center-point to near the top surface. The packaged bricks were processed in steam/air media at two temperatures (121.1"C and 1156°C) and two levels of superimposed air overpressure (corresponding to 65% and 75% steam). With the exception of the highest level of over-pressure, (121.1"C, 65% steam content), entrapped air volumes > 20 mL reduced heating rates and lethality, and shifted the cold spot from the geometric center. At 60 mL of entrapped air the point of least lethality was near the brick surface.ing may pose health risks, while over-processing reduces product quality. Several variables contribute to the effect of gas volume in pouches (pouch size, type, shape and size of food, degree of vacuum, method of packing, processing temperature and type of heating medium), and general guidelines do not exist related to the required retort over-pressure and location of the least processed region in a packaged food.The objectives of this research were (1) to examine the effect of entrapped air on the heating rate and lethality at various locations inside test packages, and (2) to identify the least processed region (cold spot) within the test packages and the accumulated lethality at the cold spot during over-pressure processing in a steam-air medium.
Temperature and heat distribution studies were carried out in a single basket horizontal water cascading retort at two temperatures and two air over‐pressure levels under fully loaded operating conditions. Various heat transfer parameters (heating and cooling rate indices, fh and fc), lag factors (jch and jcc) and process lethality (Fo) were used as indicators of the retort performance. Time‐temperature data gathered from 24 LexanTM transducers were used for calculation of the heating and cooling rate indices as well as lethality. There were significant variations in the temperature distribution and heat transfer parameters at the different tray levels; however, these variations did not contribute to large variations in the accumulated overall process lethality.
A good 4D image shows the effect on the seismic of production-related changes from within and sur-rounding a reservoir. It is well understood that the quality of 4D images is driven by two main ingredients: the quality of the acquisition and the quality of the processing. While 4D acquisition has been taking the limelight recently, the evolution of 4D processing algorithms has been steadily, and perhaps quietly, enhancing the quality of 4D images, including data acquired before the advent of carefully designed, dedicated 4D surveys. Using data from the Foinaven Field, one of three BP-operated fields in the West of Shetlands area, this paper shows how such improvements in processing technology over the last decade have enhanced the quality of the 3D imaging, the 4D seismic difference image, and improved the 4D repeatability.
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