Quantity of standard air to be cooled. Active coil face velocity can vary from 100 to 50% of design (440 to 220 fpm 2.2 to 1.1 m/s). Coil Face velocity (fpm) 4 GENERAL 1 To calculate unit dimension, each "Module" = 342mm Eg YSM / YBM 40x60 Height : (4x342 + 58 +100)mm Width : (6x342 + 58)mm Eg YDM / YCBM 40x60 Height : (4x342 + 108 + 100)mm Width : (6x342 + 108)mm NOTE : 100mm unit base to be included when calculate for unit height dimension c. spiral fins in lieu of plate fin type coils . The other consequence of dropping airflow is lower overall sensible capacity and therefore a drop in EER and SEER rating. 3 evaporator Coil types ... (Figure 2) is used for face control. A heat exchanger, with or without extended surfaces, through which either hot water, hot aqueous ethylene or propylene glycol solutions, or steam is circulated for the purpose of sensible heating of a forced-circulation air stream. Coil face dimensions In designing an evaporator for a particular requirement, the factor which most influences its dimensions is the volume flow rate of air to be cooled. Entering air wb and db temperature. The actual DX coil furnished for the system was 8 row, 10 fpi, with a face velocity of 440 fpm (2.24 m/s), so it is very near the pressure drop of the coil required for the chilled-water system: Under 350 should be … to the compressor, a minimum velocity must be maintained in the piping so that sufficient oil is returned to the compressor sump at full and part load conditions. 5. 8.6.1 Deeper coils for higher ΔT. This is termed scfm b. The value of 500 fpm (2.5 m/s) is very commonly used for coil sizing and it works very The drain pan must be elevated to provide free drainage of con-densate and to provide ample space for installation of a trap in the drain line, to overcome pressure in the coil casing. Face Pitch is the centerline distance between two consecutive tubes in the coil face… And, it would be practically “raining” off the top of a coil 96” high. °C) m =outside diameter, (m) 5. to obtain face velocity in FPM. e. coil is located immediately upstream of bottom discharge in … The cooling coil’s air face velocity shall be sized for a nominal air face velocity not to exceed 2.0 m/s (400 fpm) for the present design conditions and 2.5 m/s (480 fpm) for the future growth capacity. Face velocity, fin spacing, finned height and latent cooling rate (SHR) are all contributory factors and differing combinations will change these affects. Governing equations and methodology The sizing of cooling coil requires solving the two energy equations of the air-side and The face velocity of air through the coil should range from 400 to 600 feet per minute. DX Coil capacity is inversely proportional to evaporating temperature. WATER VELOCITY FEET PER SECOND (FPS) WATER VELOCITY FPS* = GPM × Factor ÷ Number of Tubes Fed Tube Diameter Factor 5/8 “ OD 1.085 1/2” OD 1.704 3/8” OD 3.050 **As Water Velocity increases, the capacity of a coil increases, but so does the water resistance. Figure 4A. desired tube velocity •Number of tubes in coil face is a function of coil height •Tube sizes (3/8”, 1/2”, 5/8”) •Circuiting Options •Full or 1 –All tubes in face have equal full. Our Daikin E-F (energy-efficient) fins save energy by reducing air pressure drop as much as 33% and lowering fan brake horsepower requirements. Face velocity (Feet/Min) Pressure drop (ft H2O) Refrigerant flow rate (lbs/hr) Number of circuits In. Number of circuits Out. Coil Face Area (Sq. 500 10,000 1/2 20.25 10,000 1. Air velocity for chilled water or DX coils should never be higher than 550 feet/min. 3.3 Forced-Circulation Air Coil. Ft) Air pressure drop (inches H2O) Fins per inch. c. Air flow is greater than 25% but less than 50%, two dampers and solenoid valves will open. Face velocity is restricted to 500 fpm (2.5 m/s) to avoid carryover of condensate from the coil. Coil TD increases as indicated by the colder coil in relationship to the return air; We all know that if you have far too little airflow a system can freeze up when the coil temperature drops below 32°F. DX CALCULATION. Active coil face velocity can vary from 100 to 67% of design (440 to 295 fpm/ 2.2 to 1.5 m/s). 1.2.1.3 Integral Face and Bypass Coil. A face velocity of 500 feet per minute is generally accepted as the most desirable. When I have had to do this, I always work with a coil company. Filter Face Air Velocity (FPM) 492 Maximum Initial Resistance (Inches W.G.) The amount of superheat at the exit of the DX coil has been factory set at 10 °F for calculation purposes. •Fraction circuiting (0.25, 0.33, 0.5, 0.75) –Multiple tubes are circuited together to increase tube velocity Moving to 300-400 FPM velocity adds a small % first cost but saves big in supply fan HP over life of unit. A good rule of thumb is a minimum of: • 500 feet per minute (fpm) or 2.54 meters per second (mps) for horizontal suction and hot gas lines I provide the specifications: any required dimensions, cooling capacity or heat of rejection, face area, air velocity, etc. Type EF coils are normally furnished with two distributors and two suction connections offer-ing 50% capacity reduction capabilities. Face Control is the simplest form of capacity control. Certified Characteristics. A long narrow coil has less tubes, welding and manifold than a more square coil making it cheaper to manufacture. 1.0 Minimum MERV Rating 8 B. Anything higher and you are asking for complications. To select a coil, the following information must be determined from system requiremenst: a. - arrangement of coil in relationship to the direction of the airflow - minimum and maximum number of rows - minimum and maximum number of tubes per row - minimum and maximum finned length. All DX evaporator coils and heat pump condenser coils include rifled tube enhancements and refrigerant distributors that ensure proper refrigerant distribution into the coil. Type II – Pleated panel filters 1. scfm fpm face vel. The 2.5 m/s rule for sizing cooling coils is adequate to keep water droplets from leaving the outer edge of the discharge side of the coil (carryover). Typical Dry Coil Pressure Drop in inches of H2O at 500 fpm Rows 90 fins/ft 120 fins/ft 150 fins/ft 168 fins/ft AAON DX coils are designed Description The filter media shall be bonded to a sturdy water-resistant coated beverage board filter frame to fit industry standard size filter racks. k A dx hPdx T T dx dx (5) and 2, 2,, 1 kx ()0 S kx f kx dT dT hPdA T T dx A dxdxkA (6) or 2, 2 2 (ln ) kx ()0 S dT dTdA mT T dx dx dx (7) where 2 f kx, hP m kA (8) Both P and A kx, are the function of x or a variable cross section. The maximum face velocity for cooling coils in both custom and emi-customs units shall be limited to 450 FPM. 1.2.1.2 Forced-Circulation Air-Heating Coil. A coil for use in an air stream whose circulation is caused by a difference in pressure produced by a fan or blower. In the direct expansion or DX types of air central conditioning plants the air used for cooling space is directly chilled by the refrigerant in the cooling coil of the air handling unit. A type of Coil which has damper(s) The coil company engineers come back with choices available to achieve the design: coil depth, fin spacing, number of passes, etc. S. Tredinnick, G. Phetteplace, in Advanced District Heating and Cooling (DHC) Systems, 2016. minimum of 6 inches 5 E N 14 06 C 24.00 x 144.00 . 372 Heat Exchangers Basics Design Applications Where, k g l = minimum free-flow air area, (m 2) _ = mass flow rate of air through the cooling coil, (kg/s) J _ =dynamic viscosity of air (kg/m.s) _ =thermal conductivity of air (W/m. Always question unit design and operation if they request 40% Actual face velocity = = 494 fpm. casing and headers (a minimum of 10 inches be-yond the leaving face of the coil). face velocity through the coil and ensuring proper drainage are essential to prevent moisture carryover. Second, the drain pan in the bottom of the unit for a 96” high coil would be enormous. Super heat %Ref DP/TD. 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