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ฐานข้อมูล K-Factor ของฟิตติ้ง

สัมประสิทธิ์การสูญเสีย (K-factor) สำหรับฟิตติ้ง วาล์ว และอุปกรณ์ประกอบท่อ ใช้ในสมการการสูญเสียรอง: hm = K V2/2g

37 จาก 37 ฟิตติ้ง
ประเภทฟิตติ้งรูปแบบK Factorหมวดหมู่แหล่งอ้างอิงหมายเหตุ
90 deg ElbowStandard radius (r/D = 1)
0.90
(0.7-1.0)
elbowCrane TP-410Screwed fitting. K = 30 f_T for standard radius.
90 deg ElbowLong radius (r/D = 1.5)
0.60
(0.4-0.7)
elbowCrane TP-410K = 20 f_T. Most common welded elbow in process piping.
90 deg ElbowShort radius (r/D = 0.5)
1.50
(1.2-1.8)
elbowIdelchikTight bend. Higher loss than standard. Avoid where possible.
90 deg ElbowMitre (no vanes)
1.10
(1.0-1.3)
elbowCrane TP-410Sharp corner. Used where fabrication convenience outweighs losses.
90 deg ElbowMitre (with vanes)
0.20
(0.15-0.25)
elbowIdelchikTurning vanes dramatically reduce losses in rectangular duct bends.
45 deg ElbowStandard radius
0.40
(0.3-0.5)
elbowCrane TP-410K = 16 f_T. Approximately half the loss of a 90-degree elbow.
45 deg ElbowLong radius
0.20
(0.15-0.25)
elbowCrane TP-410Welded. Low loss fitting for direction changes.
180 deg Return BendStandard
2.20
(1.5-2.5)
elbowCrane TP-410K = 50 f_T. High loss due to complete flow reversal.
TeeBranch flow (diverging)
1.80
(1.0-2.0)
teeCrane TP-410K = 60 f_T. Flow splitting into branch. Higher loss than run-through.
TeeRun-through (line flow)
0.60
(0.3-0.9)
teeCrane TP-410K = 20 f_T. Flow continuing straight through the tee.
TeeBranch flow (converging)
1.20
(0.8-1.5)
teeCrane TP-410Flow merging from branch. Slightly less loss than diverging.
CrossBranch flow
2.00
(1.5-2.5)
teeIdelchikFour-way intersection. Rarely used in modern piping.
ReducerConcentric (gradual contraction)
0.15
(0.05-0.3)
reducerCrane TP-410K depends on area ratio (d/D)^2 and cone angle. Values for 20-40 degree cone.
ReducerSudden contraction (d/D = 0.5)
0.37
(0.3-0.5)
reducerIdelchikK = 0.5(1 - (d/D)^2). Based on smaller (downstream) velocity head.
ExpansionGradual (diffuser, 7 deg cone)
0.15
(0.1-0.25)
reducerMillerOptimal cone half-angle 3-4 degrees. K based on upstream velocity head.
ExpansionSudden expansion (D/d = 2)
0.56
(0.4-0.8)
reducerBorda-CarnotK = (1 - (d/D)^2)^2. Exact from momentum theory. Based on smaller (upstream) velocity.
Pipe EntranceSharp-edged (flush)
0.50
entranceCrane TP-410Pipe flush with tank wall. Most common entrance condition.
Pipe EntranceRe-entrant (projecting)
0.78
(0.5-1.0)
entranceCrane TP-410Pipe projecting into tank. Additional vena contracta effect.
Pipe EntranceWell-rounded (r/D > 0.15)
0.04
(0.03-0.1)
entranceIdelchikBell-mouth entrance. Very low loss. Used in pump suction piping.
Pipe EntranceSlightly rounded (r/D = 0.05)
0.25
(0.1-0.3)
entranceIdelchikSmall radius on entrance edge significantly reduces loss from sharp-edged.
Pipe ExitSharp-edged (into tank)
1.00
exitCrane TP-410All kinetic energy is lost. K = 1.0 regardless of exit geometry.
Pipe ExitSubmerged discharge
1.00
exitFundamentalVelocity head is fully dissipated. Same as sharp-edged exit.
Gate ValveFully open
0.17
(0.1-0.2)
valveCrane TP-410K = 8 f_T. Very low loss when fully open. Primary isolation valve.
Gate Valve75% open
0.90
valveCrane TP-410Loss increases rapidly as valve closes. Not suitable for throttling.
Gate Valve50% open
4.50
valveCrane TP-410Very high loss. Avoid operating gate valves in partially open position.
Globe ValveFully open
10.00
(6-15)
valveCrane TP-410K = 340 f_T. High loss due to tortuous flow path. Good for throttling.
Ball ValveFull bore, fully open
0.05
(0.03-0.1)
valveCrane TP-410Very low loss. Quarter-turn operation. Common replacement for gate valves.
Ball ValveReduced bore, fully open
0.15
(0.1-0.5)
valveCrane TP-410Port diameter smaller than pipe. K depends on area ratio.
Butterfly ValveFully open
0.25
(0.2-0.5)
valveCrane TP-410K = 45 f_T. Disc always in flow path. Good for large diameter throttling.
Check ValveSwing type
2.00
(1.0-2.5)
valveCrane TP-410K = 100 f_T. Prevents backflow. Higher loss than other valve types.
Check ValveLift type
10.00
(5-15)
valveCrane TP-410K = 600 f_T. Globe-style body. Use only in horizontal pipe.
Check ValveWafer (dual plate)
0.80
(0.5-1.5)
valveManufacturerLow profile. Lower loss than swing check. Suitable for vertical installation.
StrainerY-type (clean)
2.00
(1.5-3.0)
otherManufacturerClean strainer. Loss increases as screen fouls. Monitor differential pressure.
StrainerBasket type (clean)
1.50
(1.0-2.5)
otherManufacturerLarger screen area than Y-type. Used in pump suction lines.
Flow MeterOrifice plate (beta = 0.5)
7.50
(5-30)
otherISO 5167Permanent pressure loss depends on beta ratio (d/D). Higher beta = lower loss.
Flow MeterVenturi (beta = 0.5)
0.50
(0.3-1.0)
otherISO 5167Much lower permanent loss than orifice. Recovers most of the differential pressure.
Coupling / UnionThreaded
0.08
otherCrane TP-410Negligible loss for welded or flanged joints (K ~ 0).

หมายเหตุ

K factor คือสัมประสิทธิ์การสูญเสียแบบไร้มิติ ใช้ในสมการ: hm = K · V2 / 2g โดย V คือความเร็วเฉลี่ย และ g คือความเร่งเนื่องจากแรงโน้มถ่วง

ค่าที่แสดงเป็นค่าทั่วไปสำหรับการไหลแบบปั่นป่วนเต็มที่ (Re > 105) ที่ Reynolds number ต่ำกว่า ค่า K อาจสูงกว่านี้

วิธีการ Crane TP-410 แสดงค่า K เป็นผลคูณของสัมประสิทธิ์แรงเสียดทานแบบปั่นป่วนเต็มที่ fT(เช่น K = 30 fT สำหรับข้อศอก 90 องศามาตรฐาน) ทำให้ K ขึ้นกับขนาด ค่าที่แสดงที่นี่เป็นตัวแทนสำหรับขนาด DN50-DN150

แหล่งอ้างอิง: Crane TP-410 (2018), Idelchik Handbook of Hydraulic Resistance (ฉบับที่ 3), Miller Internal Flow Systems (1990), ISO 5167

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