This app was inspired by a data interpolating app Charlie Bartlett (aka Icemeister) wrote. Charlie passed away on August 25, 2021.

The purpose of the app was to allow the user to input data from a compressor or condensing unit data sheet and allow the computer to calculate its capacity at any point within the range of the data without the need to "eyeball" the value. The user enters data having 2 independent variables, data defined by both a row and column. In the case of a condensing unit, the 2 independent variables would normally be evaporator and ambient temperatures, and the dependent variable capacity. The dependent variable could also could be the power consumed by the unit or its operating condensing pressure or temperature.

Charlie's app only allowed for 4 data points, the minimum required for a linear interpolation of data having 2 independent variables. It occurred to me why not write an app that would allow the user to define the number of rows and columns and dynamically create the table to enter this data. In addition, generate a chart of the data the user could save, and have the app employ more sophisticated interpolation techniques given sufficient data.

I have provided an Example button to get you started. For either independent variable, column or row, providing 2 data points will be linearly interpolated, the best that can be done. 3 data points will be interpolated with a quadratic equation, and 4 data points will be interpolated with a cubic equation. Data points greater than 4 will be handled with a piecewise cubic spline. My app currently allows a maximum of 6 data columns and 10 data rows (60 data points). Right click on the chart and it can be saved as a .png image file.

I've also included an interpolation app for unit coolers. Note that it allows only 1 independent variable (evaporator temperature) at the rated temperature difference (TD). The app will assume unit cooler capacity is proportional to its rated TD. Also note that it will allow for a single data point. Many medium temperature unit coolers only provide for a rating point at a 25°F evaporator temperature. The intent here is the unit cooler rating does not change in the normal range of medium temperatures (above freezing). If you plan to use the "System Balance" app, you will likely want to provide an evaporator temperature range for this app to work with. My medium temperature unit cooler examples show how to do this.

The "System Balance" app will plot both compressor or condensing unit data and unit cooler data on 1 chart. This app allows the user to find the balance point of the system.