If you have an iPhone, subscribe to the podcast HERE, and if you have an Android phone, subscribe HERE. Learn more about the HVACR Training Symposium or buy a virtual ticket today at. Unique duct challenges with inverter-driven systemsĬheck out Joey’s training, social media, and contact information at.Communicating with customers about airflow issues.Learning from other educators as an educator.Joey’s HVAC beginnings in the Navy and current work in education.We can start by looking at things that can improve system performance at the equipment, like filtration we can think of the equipment as the heart and the duct system as arteries (with static pressure as blood pressure), and the equipment also has the biggest pressure drop. Temperature and Pressure Online calculator, figures and tables showing specific heat, C P and C V, of gasous and liquid ammonia at temperatures ranging from -73 to 425☌ (-100 to 800☏) at pressure ranging from 1 to 100 bara (14.5 - 1450 psia) - SI and Imperial Units. Some technicians also aren’t properly trained to position their static pressure probes appropriately to measure total external static pressure, which leads to faulty readings and misinformed diagnoses. Bypass dampers are also commonly misapplied. In many cases, proper duct design would solve problems without the need for balancing dampers. We also need to keep in mind that flex ducts need to be as straight and tight as possible, and it’s usually best if we slightly upsize them (compared to sheet metal).Įven though balancing dampers aim to solve airflow problems, they often lead to other issues when installed and used incorrectly. In residential HVAC, many duct systems aren’t adequately planned out, and the airflow can’t overcome restrictions like filters. In many cases, people focus too heavily on the equipment when diagnosing airflow problems sometimes, the equipment simply can’t perform as it should due to a poorly designed duct system. This is all the cooling the evaporator was designed for, so, if we are getting 400 Btu/min of cooling from the system, we must be moving, 400÷745.4 lbm of refrigerant. We sincerely hope you enjoy these new features.Joey Henderson joins the podcast to talk about airflow and how we can get air where it needs to go.ĭuct design is one of the subjects that fuel Joey’s passion for HVAC. The specific enthalpy of the evaporator, or refrigerant effect, is the difference between 182 Btu/lbm and 108 Btu/lbm, or, 74 Btu/lbm. If a riser (vertical pipe) is present in the wet return line, you can also plot/indicate the minimum recommended riser mass flow corresponding to a Kutateladze number of 3.2 (the normally used limit for backflow in a riser): As opposed to simple steam tables, the calculators support ranges and. Alternatively, you can also add it to the Coolselector®2 report by selecting it as an add-on to the standard generated features:įurther to the log(p)-h diagrams, Coolselector®2 v3.0.0, now allows you to vary capacity by varying mass flow or by varying circulation rates when plotting a performance curve for a selection in the wet return line. Knovels steam calculators provide a full implementation of the 2012 cumulative. Using the buttons at the top of the screen when viewing the log(p)-h diagram, will allow you to copy or print the diagram. Calculates saturated liquid and gas properties for a given pressure or temperature using the IAPWS Industrial Formulation 1997. Please be aware that using REFPROP with Coolselector®2 requires that you have REFPROP 9.0 or newer installed. from REFPROP, you can draw the log(p)-h diagrams for these as well by changing your preferences for refrigerant equations by going to the menu “Options | Preferences | Edit Preferences | Refrigerant equations”. However, should you choose to use another refrigerant – or a refrigerant mix – i.e. The log(p)-h diagrams are all based on data from ASEREP (v3.5.0). In the liquid-vapor region in Figure 11, water and steam exist together. A P-h diagram can be constructed for any pure substance.Like the P-n diagram, there are regions on a P-h diagram in which two phases exist together. The log(p)-h diagrams look like this (e.g. Figure 11 is the P-h diagram for pure water. Alternatively, you can view all available log(p)-h diagrams for each refrigerant by going to the “Tools” menu and choosing “Log(p)-h diagrams”:
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