ASHRAE and SNAME T&R 4-16 (2015) use a formula for sensible heat gain from equipment operated by electric motors as follows: q_em = 2545*(P/E_M)*F_UM*F_LM
where
q_em = heat equivalent of equipment operation, Btu/h
P = motor power rating, hp
E_M = motor efficiency, decimal fraction <1.0
F_UM =...
I have reviewed a number of forum discussions and posted guidelines regarding pump selection and pump nozzle sizing, and most appear to indicate that pump nozzle sizing is solely a product of the pump manufacturer's design and need not be considered in the system design and/or calculations for...
A colleague of mine says ASHRAE duct design analysis cannot be relied upon for air velocities in excess of 12,000 fpm. As evidence he references ASHRAE's Friction Chart for Round Duct (See 21.8, Figure 9 in 2009 ASHRAE Handbook-Fundamentals) which only goes up to 12,000 fpm. Is it true that a...
I am designing a closed loop cooling system for multiple consumers at varying heights above baseline. The system will include a vented (open top) expansion tank to account for fluid expansion due to temperature differentials. The bottom of the expansion tank will connect to the suction side of...
Looking for a standard or publication stating maximum inlet velocity recommendations/restrictions for heat exchangers or different varieties. I am designing a cooling water system where one of the consumers specifies 185 GPM and DN 50 connections to the heat exchanger. Inlet velocity is in...
I need some direction on velocity head for calculation of centrifugal pump TDH. Is the velocity to be used that measured at the pump discharge nozzle or at the pipe connected to the nozzle (usually larger than the pump nozzle)? Isn't the velocity head at the pump nozzle included by the...
The marine vessel being designed has multiple cargo tanks and multiple cargo pumps. Initially during unload all pumps unload one tank (same tank) until level of tank is low then operators open second tank. These cargo pumps will cavitate (NPSHr>NPSHa) when pumping from single tank at low cargo...
We have a customer who wants to use a plate heat exchanger to cool marine diesel oil. In my experience shell and tube heat exchangers have been used for MDO cooling. A plate heat exchanger seems to be more prone to leakage than shell and tube. Does anyone have any experience with plate heat...
A system my company is designing requires a heat exchanger for cooling #2 diesel fuel returning from a marine engine. The Owner preference is to use a plate heat exchanger for the application which Alfa Laval has quoted model M6-FG. Our company has designed similar engines arrangements in the...
Is there a maximum RPM for a centrifugal pump? I was just quoted a centrifugal sea water pump operating at 6756 RPM. Wont it wear out quickly at this speed? Pump material is 2205 duplex stainless.
How can I determine the pressure loss through an open pipe end where the end of the pipe is smashed? See attached for pictorial representation. Would this be best analyzed as an orifice...
This system has multiple pieces of equipment requiring cooling water from a closed loop circuit of fresh water utilizing a FW/SW heat exchanger. Each piece of equipment requires different flow rate and are connected in parallel to each other. Some units are supplied with electrically actuated...
How does specific gravity affect the head and pressure of a centrifugal pump? I was under the assumption that pressure and head were synonymous? But appears that head is constant with changes in specific gravity while pressure is directly related to specific gravity. As is hp.
I have seen pump suction velocity limit recommendations of between 5 - 7 ft/s. Assume this is for the suction pipe, however what are the velocity limits at the pump flange? Goulds model 3196 centrifugal pump appears to have very high velocities at the pump inlets. For example the 1.5x3-10 has...
Do ABS or USCG have regulations citing the proper overboard discharge height for a bilge pump? I have been looking through ABS and CFR and have yet to find any regulations regarding discharge height. Any direction on where I might find some info on this is appreciated.
I am working on a hydraulic system for a boom slew actuator and am unsure what the attached symbols represent. The first symbol was in a hydraulic line between the actuator cylinders and the directional valve. The other is a solenoid operated directional valve that has extra geometry which I...
The senior engineer at my company uses the following estimated constants to calculate the amount of fuel used by an engine.
.0.378 lbs/hr-h
0.282 lbs/kw-h
I have been using the data from the specification sheets for example from the Cat C18 engine and when I try to get this constant I am...
Hello,
I am looked for resistance coef (k) values for calculating pressure of a hole in the wall of a pipe. Is this the same as k values for an orifice in a pipe? This is for a design of cooling spray around a shaft. The cooling water will be directed through a circular pipe around the shaft...
My company is preparing plans for installation of an additional sea chest on a large vessel. The sea chest in question will be located in a ballast tank with reach rod access to the ballast supply butterfly valve. ABS regulations require means for clearing the strainer plates which is...
