Home › B.Tech Civil › civilengineering › Concreting Equipment › Vacuum cooling of aggregates uses the lower boil…
Vacuum cooling of aggregates uses the lower boiling point of water at sub-atmospheric pressure plus the heat absorbed when water vapourises. Steel silos under a vacuum of about 6 mm Hg lower aggregate from about 43 °C to approximately:
Answer & Solution
Correct answer: B.
1. The aggregate must be processed moist so its free water can evaporate.
2. The unit gives steel silos of 90–270 t capacity under 6 mm Hg vacuum.
3. Over a 45-minute operational cycle this drops initial 43 °C aggregate to about 10 °C final.
4. The vacuum is applied via a side chamber by steam-fed pumps.
5. 2 °C and 20–30 °C miss the average final temperature reported.
_Source: IGNOU Concrete Technology, Unit 7 "Concreting Equipment" (Mixers, Cableways, Batchers, Buckets, Pre/Post Cooling)._
Related questions
Refrigeration plant capacity for pre-cooling of mass concrete is expressed in tons of refrIn the heat-balance equation, the specific heat of cement is generally taken between:In the heat-balance equation Eq. 7.2 for ice quantity, the latent heat of fusion of ice isIn the post-cooling pumping plant, each pipe coil is supplied at a flow rate of approximatThe unit specifies that individual embedded pipe runs may range from 180 to 360 m, with a Embedded post-cooling pipes carry circulating cool water through hardened concrete. The unCement is normally batched dry. To avoid moisture condensation that would adversely affectCoarse aggregate is cooled by inundation in a tank of chilled water. With water at 2 °C, e