ti:o p sut chn khng

ti:o p sut chn khng

I HC QUC GIA THNH PH H CH MINHTRNG I HC BCH KHOAB MN CNG NGH NHIT LNH

BO CO O LNG NHIT

GVHD:Nguyn Th Minh TrinhNHM:7

TP. H CH MINH, THNG 4/2015

TI: O P SUT CHN KHNG

SINH VIN THAM GIA:NGUYN NH KHANG21201583L XUN NHT HIU21201091HONG VIT HNG21101419

MC LC

I.P SUT:61.nh Ngha:62. n v o p sut:6II.CHN KHNG:71.Lch s chn khng:72.nh ngha:83.Phn loi:8III.PHNG PHP O V DNG C O P SUT CHN KHNG:91.Phng php o:92.Dng c o p sut chn khng:9IV.NG DNG TRONG K THUT V I SNG:111.ng Venturi:112.Bm ht chn khng:123.Phng php ht chn khng trong iu tr tn thng ty sng:134.Phng php HCK trong xy dng:14Ngun ti liu:16

I. P SUT:1. nh Ngha: p sut c nh ngha l lc do lu cht tc dng vung gc ln mt n v din tch b mt, k hiu l P:P= (kg/cm2)C 3 tnh cht: - p sut lun lun tc ng vung gc vi thnh bnh tip xc vi lu cht. - Ti mt im bn trong lu cht tnh, p sut theo mi phng u nh nhau . - nh lut Pascal: trong bnh kn, gia tng p sut c truyn i khp mi im trong lu cht. 2. n v o p sut: 1 Pa = 1 N/m2 1 mm Hg = 133.322 N/m2 1 mm H20 = 9.8 N/m2 1 bar = 105 N/m2 1 at = 9.8 x 104 N/m2p sut tuyt i v p sut d C 2 phng php xc nh p sut. - Phng php o p da vo chn khng tuyt i l p sut tuyt i.- Phng php o p da vo p sut kh quyn l p sut d -Mi quan h p sut tuyt i v p sut d nh sau: p sut d = p sut tuyt i - p sut kh quyn Pd = Ptd Pb. p sut chn khng l hiu s gia kh p v p sut tuyt i: Pck = Pb Ptd Chn khng tuyt i khng th to ra c.

II. CHN KHNG:1. Lch s chn khng:Hn 25 th k qua, chn khng c con ngi gn cho nhiu khi nim khc nhau.Theo quan nim ca cc nh khoa hc thi c i th k XV, m tiu biu l Democrite- cha ca thuyt nguyn t, cho rng chn khng l khng gian khng cha vt cht, trng rng, hon ton khng c g. Qua , c ngha l vi th tch khc khng, nhng khi lng bng khng dn n nng lng bng khng th p sut bng khng. Mt th k sau, Aristote li ph nhn chn khng v ca ngi thin nhin. Thin nhin c mt khp mi ni, cho rng khng gian cha y ete v tr-cht tinh ty tuyt vi, n c mt mi ni, mi chn. Vy, chn khng khng th tn ti, v nu c th chuyn ng ca mt vt s phi tc thi hay bt tn. Nhng t duy nim c tnh trit hc v chn khng. trng rng, h v thng tr t duy ca th gii Rp, La M, Hy Lp ch b nh khi c s ra i khoa hc thc ngim ca Gallile(1564-1642),Pascal(1623-1662), Torricelli(1608-1647) TK XVII. D bn cht ca chn khng cha c sng t nhng k t , chn khng mi i dn vo hin thc cuc sng.

Nhng n nm 1654, sau th nghim ca Qu cu Magdeburg Otto Von Guericke tin hnh ti bang Magdeburg, nc c,qu hng ng, chn khng mi thc s c hiu ng v bt u phc v sn xut. C th ni, ng l ngi t nn tng, l cha ca chn khng. Ni v th nghim Qu cu Magdeburg. Mi hc sinh u c hc trung hc, trong th nghim ny, c 16 con nga- mi bn 8 con ko mt bn cu kim loi mi nhn, p st vo nhau v c rt ht khng kh bn trong bng chic my ht chn khng cng do Otto ch to vo nm 1650. Qua th nghim ny, con ngi mi thy c sc p to ln ca kh quyn ln mt t nh th no.

Ngy nay, l thuyt lng t khng nh Rng: Do s ng n ca Nguyn l bt nhm lun c s dao ng khi lng v nng lng (d rt nh) trong lng chn khng. Ngha l, nhng ht mang nng lng vn tn ti trong chn khng. Chng to ra p sut trong lng chn khng, gi l p sut lng t chn khng. V, thc t chng minh Khng tn ti mi trng chn khng hon ho nh l thuyt.

2. nh ngha:

chn khng, trong vt l thuyt c in, l khng gian khng cha vt cht. Nh vy chn khng c th tch khc khng v khi lng (v do nng lng) bng khng. Do khng c vt cht bn trong, chn khng l ni khng c p sut.Mt s l thuyt lng t cho bit khi nim chn khng theo ngha c in khng tn ti, do vi phm nguyn l bt nh. Chn khng, theo cc l thuyt ny, lun c s dao ng khi lng (v do nng lng) nh. iu ny ngha l, mt thi im no , lun c th xut hin mt cch ngu nhin cc ht c nng lng dng v mt thi im khc ht ny bin mt. Cc ht ngu nhin xut hin trong chn khng to ra mt p sut gi l p sut lng t chn khng. Cc th nghim o c p sut ny s gip khng nh chnh xc ca cc l thuyt lng t v chn khng.

Trong thc t, khng c ni no trong v tr quan st c tn ti chn khng hon ho nh l thuyt. Cc th nghim v cc ng dng thc t c th to ra cc khng gian cha t vt cht v c p sut thp. Nhng khng gian ny cng hay c gi l "chn khng" trong k thut, nh khi ni v my bm chn khng, ty theo quy c v gii hn p sut thp. Nh vy, chn khng c hiu l khong khng-thi gian c th c mt vt cht thp v/hoc rt thp. Lu , khi nim thp v rt thp y c hiu mt cch tng i...

3. Phn loi:Trng thi chn khng, do , hiu l trng thi c p sut nh hn p sut kh quyn trung bnh chun, v c chia thnh: Chn khng thp (p>100Pa) Chn khng trung bnh (100Pa>p>0.1Pa) Chn khng cao (0.1Pa>p>10-5Pa) Chn khng siu cao (p trong nhnh kn c p sut P2 v th tch: V2 . h.g.V P2 = P1 + h V2 ( P1 + h) = P1 .V1 P1 = V1 V2 Nu V2