Abod test is to be run on a sample of wastewater that has a five-day bod of 230 mg/l. if the initial do of a mix of distilled water and wastewater is 8.0 mg/l, and the test requires a decrease in do of at least 2.0 mg/l with at least 2.0 mg/l of do remaining at the end of the five days, what range of dilution factors (p) would produce acceptable results? in 300 ml bottles, what range of wastewater volumes could be used?

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

At 12 noon, the count in a bacteria culture was 400; at 4: 00 pm the count was 1200 let p(t) denote the bacteria cou population growth law. find: (a) an expression for the bacteria count at any time t (b) the bacteria count at 10 am. (c) the time required for the bacteria count to reach 1800.

How to increase the thermal officiency of an ideal simple rankino cycle? among these methods, which one is the best and why?