Address HSPF2 calculation problems for multispeed DX system #10618
There are no files selected for viewing
| Original file line number | Diff line number | Diff line change |
|---|---|---|
|
|
@@ -6332,17 +6332,17 @@ namespace StandardRatings { | |
| Real64 q_H0_low = Q_H0_Low(spnum); | ||
| Real64 q_H1_low = Q_H1_Low(spnum); | ||
| Real64 q_H2_int = Q_H2_Int(spnum); | ||
| Real64 q_H1_full = Q_H1_Full(spnum + 1); | ||
| Real64 q_H2_full = Q_H2_Full(spnum + 1); | ||
| Real64 q_H3_full = Q_H3_Full(spnum + 1); | ||
| Real64 q_H4_full = Q_H4_Full(spnum + 1); | ||
| // Equation 11.177 AHRI-2023 | ||
| //?? (replaced 62 with 35) in Ratio expression // (t=>35-47/62-47) | ||
| Real64 q_35_low = // q_H1_low + (q_H0_low - q_H1_low) * ((t - (8.33)) / (1.66 - (8.33))); | ||
| q_H1_low + (q_H0_low - q_H1_low) * ((1.67 - (8.33)) / (16.67 - (8.33))); | ||
|
|
||
| // Equation 11.191 AHRI-2023 | ||
| Real64 N_Hq = (q_H2_full != q_35_low) ? min(1.0, (q_H2_int - q_35_low) / (q_H2_full - q_35_low)) : 0.0; | ||
|
There was a problem hiding this comment. Modified to allow evaluation of the HSPF2 with flat heating capacity modifier curves function of temperature. There was a problem hiding this comment. This fixes #10651 FWIW, and this looks like undefined behavior, but I was finding that in a release build with no floating point exceptions enabled, when you had the same Cap FT / Fflow curves, N_Hq was 0 but N_HE was 1. |
||
| N_Hq = max(0.0, N_Hq); | ||
| // Equation 11.190 AHRI-2023 | ||
| Real64 M_Hq = (q_H0_low - q_H1_low) / (16.66 - 8.33) * (1.0 - N_Hq) + (q_H2_full - q_H3_full) / (1.66 - (-8.33)) * N_Hq; | ||
|
|
@@ -6351,17 +6351,17 @@ namespace StandardRatings { | |
| Real64 p_H0_low = P_H0_Low(spnum); | ||
| Real64 p_H1_low = P_H1_Low(spnum); | ||
| Real64 p_H2_int = P_H2_Int(spnum); | ||
| Real64 p_H1_full = P_H1_Full(spnum + 1); | ||
| Real64 p_H2_full = P_H2_Full(spnum + 1); | ||
| Real64 p_H3_full = P_H3_Full(spnum + 1); | ||
| Real64 p_H4_full = P_H4_Full(spnum + 1); | ||
|
There was a problem hiding this comment. The full electric power input must be evaluated at the next available speed, not at the current speed. It should be different from the low speed. |
||
| // Equation 11.178 AHRI - 2023 | ||
| //?? (replaced 62 with 35) in Ratio expression (t=>35 F-47/35-47) | ||
| Real64 p_35_low = // p_H1_low + (p_H0_low - p_H1_low) * ((t - (8.33)) / (1.66 - (8.33))); | ||
| p_H1_low + (p_H0_low - p_H1_low) * ((1.67 - (8.33)) / (16.67 - (8.33))); | ||
|
|
||
| // Equation 11.194 AHRI-2023 | ||
| Real64 N_HE = (p_H2_int != p_35_low) ? min(1.0, (p_H2_int - p_35_low) / (p_H2_full - p_35_low)) : 0.0; | ||
|
There was a problem hiding this comment. It was modified to allow the evaluation of the HSPF2 with flat heating capacity modifier curves function of temperature. |
||
| N_HE = max(0.0, N_HE); | ||
|
|
||
| // Equation 11.193 AHRI-2023 | ||
|
|
@@ -6375,35 +6375,63 @@ namespace StandardRatings { | |
| Real64 q_hs(0.0); | ||
| Real64 p_hs(0.0); | ||
| // Low Speed | ||
| if (t >= 8.33) { | ||
| Real64 ratio = // (t - 8.33) / (16.67 - 8.33) | ||
| (t - HeatingOutdoorCoilInletAirDBTempRated) / | ||
| (HeatingOutdoorCoilInletAirDBTempH0Test - HeatingOutdoorCoilInletAirDBTempRated); | ||
| // equation 11.179 | ||
| q_low = Q_H1_Low(spnum) + ((Q_H1_Low(spnum) - Q_H3_Full(spnum)) * ratio); | ||
| // equation 11.182 | ||
| p_low = P_H1_Low(spnum) + ((P_H1_Low(spnum) - P_H3_Full(spnum)) * ratio); | ||
| } else if (t >= 1.67 && t < 8.33) { | ||
| Real64 ratio = // (t - 1.67) / (8.33 - 1.67) | ||
| (t - HeatingOutdoorCoilInletAirDBTempH2Test) / | ||
| (HeatingOutdoorCoilInletAirDBTempRated - HeatingOutdoorCoilInletAirDBTempH2Test); | ||
| // equation 11.180 | ||
| q_low = Q_H2_Int(spnum) + ((Q_H0_Low(spnum) - Q_H1_Low(spnum)) * ratio); | ||
| // equation 11.183 | ||
| p_low = P_H2_Int(spnum) + ((P_H0_Low(spnum) - P_H1_Low(spnum)) * ratio); | ||
| } else if (t < 1.67) { | ||
| // for now Q_H2_Int is replaced with Q_H_Int, no equation for the later | ||
| // equation 11.181 | ||
| q_low = Q_H2_Int(spnum); | ||
| // equation 11.184 | ||
| p_low = P_H2_Int(spnum); | ||
|
There was a problem hiding this comment. It was modified the equations used to calculate delivered heat and energy input at the |
||
| } | ||
|
|
||
| // High Speed | ||
| if (t <= -15.0) { | ||
| Real64 ratio = // ((t - (-15.0)) / (8.33 - (-8.33))); | ||
| (t - HeatingOutdoorCoilInletAirDBTemp_H4FullTest) / | ||
| (HeatingOutdoorCoilInletAirDBTempRated - HeatingOutdoorCoilInletAirDBTempH3Test); | ||
| // equation 11.205 | ||
| q_hs = Q_H4_Full(spnum + 1) + ((Q_H1_Full(spnum + 1) - Q_H3_Full(spnum + 1)) * ratio); | ||
| // equation 11.206 | ||
| p_hs = P_H4_Full(spnum + 1) + ((P_H1_Full(spnum + 1) - P_H3_Full(spnum + 1)) * ratio); | ||
| } else if ((t > -15.0) && (t < -8.33)) { | ||
| Real64 ratio = // ((t - (-15.0)) / (-8.33 - (-15.0))); | ||
| (t - HeatingOutdoorCoilInletAirDBTemp_H4FullTest) / | ||
| (HeatingOutdoorCoilInletAirDBTempH3Test - HeatingOutdoorCoilInletAirDBTemp_H4FullTest); | ||
| // equation 11.203 | ||
| q_hs = Q_H4_Full(spnum + 1) + ((Q_H3_Full(spnum + 1) - Q_H4_Full(spnum + 1)) * ratio); | ||
| // equation 11.204 | ||
| p_hs = P_H4_Full(spnum + 1) + ((P_H3_Full(spnum + 1) - P_H4_Full(spnum + 1)) * ratio); | ||
| } else if ((t > -8.33) && (t < t_ob)) { | ||
| Real64 ratio = //((t - (-8.33)) / (1.67 - (-8.33))); | ||
| (t - HeatingOutdoorCoilInletAirDBTempH3Test) / | ||
| (HeatingOutdoorCoilInletAirDBTempH2Test - HeatingOutdoorCoilInletAirDBTempH3Test); | ||
| // equation 11.201 | ||
| q_hs = Q_H3_Full(spnum + 1) + ((Q_H2_Full(spnum + 1) - Q_H3_Full(spnum + 1)) * ratio); | ||
| // equation 11.202 | ||
| p_hs = P_H3_Full(spnum + 1) + ((P_H2_Full(spnum + 1) - P_H3_Full(spnum + 1)) * ratio); | ||
| } else if ((t >= t_ob) && (t <= -8.33)) { | ||
| Real64 ratio = // ((t - (-8.33)) / (8.33 - (-8.33))); | ||
| (t - HeatingOutdoorCoilInletAirDBTempH3Test) / | ||
| (HeatingOutdoorCoilInletAirDBTempRated - HeatingOutdoorCoilInletAirDBTempH3Test); | ||
| // equation 11.199 | ||
| q_hs = Q_H3_Full(spnum + 1) + ((Q_H1_Full(spnum + 1) - Q_H3_Full(spnum + 1)) * ratio); | ||
| // equation 11.200 | ||
| p_hs = P_H3_Full(spnum + 1) + ((P_H1_Full(spnum + 1) - P_H3_Full(spnum + 1)) * ratio); | ||
| } | ||
|
There was a problem hiding this comment. Modified the equations used to calculate delivered heat and energy input at the There was a problem hiding this comment. OK, so here I see the equations. I still don't know if Q_H1_Full should be the "full" capacity at the speed being evaluated or the full capacity at the next highest speed. What in the standard prompted this change? There was a problem hiding this comment. My understanding is that the next higher speed level should be used to get the full speed capacity that bounds the current There was a problem hiding this comment. But if PLR at speed x is < 1 then the full capacity at that same speed would bound the current building load. So where in the standard does it say to use the next highest speed level? There was a problem hiding this comment. In the standard, different sections may apply to this code: one for a two-speed (two-capacity) machine and another one for a variable-speed machine. They are not an exact match for a discrete-speed machine with more than the two-speed. The HSPF2 calculation is based on the variable speed section of the standard, and it requires some interpretation to fit the discrete multispeed DX heating coil model we have in EnergyPlus. It requires some judgment on how to account for the difference between the EnergyPlus model and the variable speed machine procedure in the AHRI standard. Simply, it needs interpretation of the procedure for implementation in EnergyPlus. In a variable-speed machine, you have just one full speed, like the two-speed DX cooling coil model in EnergyPlus. In the multispeed DX heating coil, your full speed is a moving target, and depending on your load, it is the next available higher-speed capacity. Let's say a given load is bound between two-speed levels; the full load should point to the higher speed level, not the lower speed. This is my interpretation of how it should be. The current full capacity assignment was to the current speed, so I changed it to the next higher-speed capacity. |
||
|
|
||
| Real64 cop_low = q_low / p_low; | ||
|
|
@@ -6469,18 +6497,30 @@ namespace StandardRatings { | |
| } else if (bl >= q_full) { | ||
| // CASE 3 : 11.2.2.3.3 AHRI-2023 | ||
| // Building Load is greater than the capacity of the unit at the Full Compressor Speed, q_full <= bl or (bl >= q_full:) | ||
| if (t <= -15.0) { | ||
| Real64 t_ratio = (t - (-15.0)) / ((8.33) - (-8.33)); | ||
| // Equation 11.205 AHRI-2023 | ||
| q_full = q_H4_full + (q_H1_full - q_H3_full) * t_ratio; | ||
| // Equation 11.206 AHRI-2023 | ||
| p_full = p_H4_full + (p_H1_full - p_H3_full) * t_ratio; | ||
| } else if (t > (-15.0) && t < (-8.33)) { | ||
| Real64 t_ratio = (t - (-15.0)) / (-8.33 - (-15.0)); | ||
| // Equation 11.203 AHRI-2023 | ||
| q_full = q_H4_full + (q_H3_full - q_H4_full) * t_ratio; | ||
| // Equation 11.204 AHRI-2023 | ||
| p_full = p_H4_full + (p_H3_full - p_H4_full) * t_ratio; | ||
| } else if (t > (-8.33) && t < t_ob) { | ||
| Real64 t_ratio = (t - (-8.33)) / (1.67 - (-8.33)); | ||
| // Equation 11.201 AHRI-2023 | ||
| q_full = q_H3_full + (q_H2_full - q_H3_full) * t_ratio; | ||
| // Equation 11.202 AHRI-2023 | ||
| p_full = p_H3_full + (p_H2_full - p_H3_full) * t_ratio; | ||
| } else if (t >= t_ob || t == (-8.33)) { | ||
| Real64 t_ratio = (t - (-8.33)) / (8.33 - (-8.33)); | ||
| // Equation 11.199 AHRI-2023 | ||
| q_full = q_H3_full + (q_H1_full - q_H3_full) * t_ratio; | ||
| // Equation 11.200 AHRI-2023 | ||
| p_full = p_H3_full + (p_H1_full - p_H3_full) * t_ratio; | ||
| } | ||
|
There was a problem hiding this comment. The current code for Case III looks incorrect based on the review of the AHRI 2023 (2020) Standard for Performance Rating of Unitary Air-conditioning & Air-source Heat Pump Equipment. This code change matches the AHRI standard and corrects the logic flaws. |
||
|
|
||
| // if not conducting H4 Test then use this block | ||
|
|
||
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
The full heating capacity must be evaluated at the next available speed, not at the current speed. It should be different from the low speed.
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
It makes sense, and I believe you, but it would be great to get a second opinion on it. Anyone have thoughts on this?
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
I don't know the standard but what will these values be used for? i.e., these would be used in some equation, so show the equation to support this change. For example, q_H1_full looks to be the capacity at speed 1 so why would we use speed 2 capacity?
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
These capacities (H1, 2, 3, 4) are used to estimate the full capacity at a specified outdoor a condition through interpolation. The full capacity is then used to bracket the
building loadto get a speed level of the machine that matches thebuilding load.