真空煲的原理是......急!10分

真空煲係利用保溫原理令煲內的溫度下降速度放慢，從而令煲內可以較長時間保持高溫而令食物煮熟。

真空煲主要由兩部份組成：一個鋼的內鍋和一個保溫外層。食物首先通過正常途徑在內鍋加熱煮熟。然後，內鍋連食物一起被放到保溫外層之中。保溫外層的設計是使熱量流失減至最小。食物與環境絕熱，被長時間保持在高溫之中。以下的圖片顯示真空煲的不同部份。





圖片參考：http://www.hk-phy.org/energy/domestic/heat_phy/images/thermal_cooker_01_c.jpg



圖片參考：http://www.hk-phy.org/energy/domestic/heat_phy/images/thermal_cooker_02_c.jpg


真空煲主要由兩部份組成：一個鋼的內鍋和一個保溫外層。

真空煲的兩個主要部份。
Vacuum flask cooking was introduced to the Asian market in the mid-1990s. The vacuum cooker is a stainless steel vacuum flask. The flasks come in various sizes ranging from 20-40 cm (8-16 in) in diameter and 25 cm (10 in) tall. A removable pot, with handle and lid, fits inside the vacuum flask. The pot and contents are heated to cooking temperature, and then sealed in the flask. The flask simply reduces heat loss to a minimum, so that the food remains at cooking temperature for a long time, and cooks without continued heating. Note that the food is not cooked in a vacuum.
Vacuum flasks appeal to Cantonese cooks because many Cantonese dishes require prolonged braising or simmering. When these cookers were first introduced in the US, they sold very quickly in the larger Asian supermarkets. The slow cooker is used for a similar purpose; but instead of minimising heat loss, sufficient heat is applied to the non-insulated slow cooker to maintain a steady temperature somewhat below the boiling point of water. A slow cooker allows any desired cooking time; the more energy-efficient vacuum flask must cook within the time taken for the food to cool below cooking temperature.
A vacuum flask cooker cooks food expending only enough energy to heat the pot and contents to cooking temperature; the food is cooked by the stored heat, as the flask drastically reduces heat lost to the environment. 10 to 20 times less energy is required to cook this way than using conventional methods without thermal insulation.
Cooking this way is convenient for people with little free time, and activities away from home. For example, a domestic user may prepare a meal, then spend many hours away from home—working at a job, for instance—returning to food ready to eat.