Figure 4B. c. leaving air wb and db temperature required. •Fraction circuiting (0.25, 0.33, 0.5, 0.75) –Multiple tubes are circuited together to increase tube velocity It is a balance between the desired capacity and the resultant 20 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 Face Pitch is the centerline distance between two consecutive tubes in the coil face… 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: The number of fins per inch is determined by the allowable air friction loss. Type EF coils are normally furnished with two distributors and two suction connections offer-ing 50% capacity reduction capabilities. This face velocity shall be based on the actual coil face area sans any safing around the coil. 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 Entering air wb and db temperature. The direct expansion or the DX type of central air conditioning system is usually used for cooling the small buildings or the rooms on the single floor. Our Daikin E-F (energy-efficient) fins save energy by reducing air pressure drop as much as 33% and lowering fan brake horsepower requirements. To select a coil, the following information must be determined from system requiremenst: a. Traditional Face Split. 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. A coil for use in an air stream whose circulation is caused by a difference in pressure produced by a fan or blower. The finned height and finned length (face area) of the coil must be chosen to give an acceptable face velocity (volume flow rate divided by face area). The maximum face velocity for cooling coils in both custom and emi-customs units shall be limited to 450 FPM. Anything higher and you are asking for complications. Air velocity: For a given cfm of air, a reduction in coil face area increases coil face velocity over the coil tubes. 1.2.1.3 Integral Face and Bypass Coil. Coils operating with all or high fresh air content are particularly vulnerable. Second, the drain pan in the bottom of the unit for a 96” high coil would be enormous. Quantity of standard air to be cooled. DX condenser coils are available with multiple rows, up to 22 fins per inch, and can be configured with interlaced or face split circuitry. to obtain face velocity in FPM. Face velocity is restricted to 500 fpm (2.5 m/s) to avoid carryover of condensate from the coil. Positive coil freeze protection must be used in … Type II – Pleated panel filters 1. 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. 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 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. Always question unit design and operation if they request 40% Add a new Section 5.12 to specify requirements for finned-tube coils in the air distribution system. 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 Face Control is the simplest form of capacity control. °C) m =outside diameter, (m) 5. DX CALCULATION. This is termed scfm b. At part load, only a portion of the coil face remains active. 3.3.1 Forced-Circulation Air-Cooling Coil. When I have had to do this, I always work with a coil company. scfm fpm face vel. Moving to 300-400 FPM velocity adds a small % first cost but saves big in supply fan HP over life of unit. - 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. c. Air flow is greater than 25% but less than 50%, two dampers and solenoid valves will open. Figure 4A. 3 evaporator Coil types ... (Figure 2) is used for face control. Coil choices include water cooling, water heating, steam, booster, evaporator and condenser. The face velocity of air through the coil should range from 400 to 600 feet per minute. 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. 1.2.1.2 Forced-Circulation Air-Heating Coil. The coil company engineers come back with choices available to achieve the design: coil depth, fin spacing, number of passes, etc. Within limits, the … Glycol % has a drastic negative effect on transfer properties making GPM, coil and piping sizing go up. 500 10,000 1/2 20.25 10,000 1. Description The filter media shall be bonded to a sturdy water-resistant coated beverage board filter frame to fit industry standard size filter racks. Governing equations and methodology The sizing of cooling coil requires solving the two energy equations of the air-side and DX Coil capacity is inversely proportional to evaporating temperature. 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. Design parameters used are: coil face velocity of 2.0 m/s, air inlet relative humidity of 90%, temperature 30 °C, refrigerant enthalpy 351 . Certified Characteristics. 5. The amount of superheat at the exit of the DX coil has been factory set at 10 °F for calculation purposes. 0.40 Minimum Rated Final Resistance (Inches W.G.) Our Daikin Hi-F (high-efficiency) fins maximize heat transfer with less fins to lower your initial cost. This temperature does not include superheat. I provide the specifications: any required dimensions, cooling capacity or heat of rejection, face area, air velocity, etc. I could turn the heat on and get delta T and use-btu output x 1.08 /delta T to obtain CFM, then use CFM /area of coil in sqft. Number of circuits Out. Ft) Air pressure drop (inches H2O) Fins per inch. 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. b. coil fin height >36”; tall coils will tend to carryover at lower velocities . The airside system is considered to be the same performance as for the chilled-water system. face velocity through the coil and ensuring proper drainage are essential to prevent moisture carryover. Local high velocities and moisture tracking causing spillage are best avoided by downstream drainage. 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. Under 350 should be … of face area per hour under peak sensible and peak dew point design conditions , considering both latent load and coil face velocity. 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. 1.0 Minimum MERV Rating 8 B. VIEW EXISTING RUNS UPLOAD TEST CSV FILE. A face velocity of 500 feet per minute is generally accepted as the most desirable. If space allows, making coil section larger to reduce velocity. Face velocity, fin spacing, finned height and latent cooling rate (SHR) are all contributory factors and differing combinations will change these affects. S. Tredinnick, G. Phetteplace, in Advanced District Heating and Cooling (DHC) Systems, 2016. d. coil face velocity >550 FPM . And, it would be practically “raining” off the top of a coil 96” high. c. spiral fins in lieu of plate fin type coils . 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. Filter Face Air Velocity (FPM) 492 Maximum Initial Resistance (Inches W.G.) The other consequence of dropping airflow is lower overall sensible capacity and therefore a drop in EER and SEER rating. Active coil face velocity can vary from 100 to 67% of design (440 to 295 fpm/ 2.2 to 1.5 m/s). Suction pressure remains low in the active circuit, thus providing a lower fin temperature and leaving air temperature in the active portion of the face. Actual face velocity = = 494 fpm. The value of 500 fpm (2.5 m/s) is very commonly used for coil sizing and it works very Face Pitch. Coil Face Area (Sq. Air velocity for chilled water or DX coils should never be higher than 550 feet/min. 8.6.1 Deeper coils for higher ΔT. Selecting a maximum face velocity will determine a minimum face size but the length to height ratio will have effect on cost. 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). Active coil face velocity can vary from 100 to 50% of design (440 to 220 fpm 2.2 to 1.1 m/s). To simplify the equation, the new dependent variable is introduced: www.intechopen.com DOWNLOAD CSV FILE. A heat exchanger, with or without extended surfaces, through which A long narrow coil has less tubes, welding and manifold than a more square coil making it cheaper to manufacture. Super heat %Ref DP/TD. e. coil is located immediately upstream of bottom discharge in … casing and headers (a minimum of 10 inches be-yond the leaving face of the coil). All DX evaporator coils and heat pump condenser coils include rifled tube enhancements and refrigerant distributors that ensure proper refrigerant distribution into the coil. 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